feat(plex): every card rail in the reader's language; an episode in a poster rail stands as its show (E30 S1b)

The grid served Hungarian titles, but every other card surface (Discover rails, the
show page's episodes, search, collections, the person page, playlists, Home's resume
rail, hero and comfort shelf) served English. The card serializers now take a
required keyword-only lang (a forgotten call site fails instead of going English), and
each of those reads takes ?lang=hu, with the language in its query key. A Hungarian
search finds an episode by its Hungarian title too.

An episode on a poster rail showed its 16:9 still cropped into a poster, titled only
with the episode name; it now shows the show's poster and name, with S·E · title under
it (option A). Plex's generic season names (Season 1, Specials) are rebuilt from the
number in the reader's language; a season with a name of its own keeps it.

Home's comfort-shelf move wrote its optimistic order to the key without the language,
which nothing read any more; it writes the query's own key.

backend/tests/test_discover.py

@@ -180,7 +180,7 @@ def test_continue_watching_merges_both_sources_by_recency(db):
     )
     db.commit()
 
-    got = rails.continue_watching(db, user)
+    got = rails.continue_watching(db, user, lang="en")
     assert [(c["source"], c["id"]) for c in got] == [("plex", "pm1"), ("youtube", "vmed")]
     assert got[0]["remaining_seconds"] == 100 * 60 - 600
 
@@ -208,7 +208,7 @@ def test_continue_watching_is_youtube_only_when_plex_is_off(db):
         ]
     )
     db.commit()
-    assert {c["source"] for c in rails.continue_watching(db, user)} == {"youtube"}
+    assert {c["source"] for c in rails.continue_watching(db, user, lang="en")} == {"youtube"}
 
 
 def test_the_resume_rail_obeys_the_channel_blocklist(db):
@@ -227,13 +227,13 @@ def test_the_resume_rail_obeys_the_channel_blocklist(db):
         )
     )
     db.commit()
-    assert [c["id"] for c in rails.continue_watching(db, user)] == ["vmed"]
+    assert [c["id"] for c in rails.continue_watching(db, user, lang="en")] == ["vmed"]
 
     db.add(BlockedChannel(user_id=user.id, channel_id=ch.id))
     db.commit()
-    assert rails.continue_watching(db, user) == []
+    assert rails.continue_watching(db, user, lang="en") == []
     # And so the hero, whose resume tier draws from that rail, has nothing to offer either.
-    assert hero.pick(db, user, "any", 0) is None
+    assert hero.pick(db, user, "any", 0, lang="en") is None
 
 
 def test_a_null_timestamp_sorts_last(db):
@@ -263,7 +263,7 @@ def test_a_null_timestamp_sorts_last(db):
         ]
     )
     db.commit()
-    got = rails.continue_watching(db, user)
+    got = rails.continue_watching(db, user, lang="en")
     assert got[0]["id"] == "vshort"
     assert len(got) == 3
 
@@ -283,7 +283,7 @@ def test_hero_prefers_resume_and_labels_the_tier(db):
         )
     )
     db.commit()
-    got = hero.pick(db, user, "any", seed=1)
+    got = hero.pick(db, user, "any", seed=1, lang="en")
     assert got["tier"] == "resume"
     assert got["card"]["id"] == "vmed"
 
@@ -302,7 +302,7 @@ def test_hero_skips_a_resume_that_does_not_fit_the_budget(db):
         )
     )
     db.commit()
-    got = hero.pick(db, user, "short", seed=1)
+    got = hero.pick(db, user, "short", seed=1, lang="en")
     assert got["tier"] == "surprise"
     assert got["card"]["duration_seconds"] <= BANDS["short"][1]
 
@@ -312,7 +312,7 @@ def test_hero_falls_back_to_the_shelf_before_guessing(db):
     user, ch = _seed_yt(db)
     db.add(ComfortPin(user_id=user.id, video_id="vmed", position=0))
     db.commit()
-    got = hero.pick(db, user, "medium", seed=1)
+    got = hero.pick(db, user, "medium", seed=1, lang="en")
     assert got["tier"] == "comfort"
     assert got["card"]["id"] == "vmed"
 
@@ -332,7 +332,7 @@ def test_hero_resolves_a_show_to_the_episode_that_would_play(db):
         )
     )
     db.commit()
-    got = hero.pick(db, user, "any", seed=1)
+    got = hero.pick(db, user, "any", seed=1, lang="en")
     assert got["tier"] == "resume"
     assert got["card"]["kind"] == "episode"
     assert got["card"]["id"] == "ps1e2"  # ep1 is finished → ep2 is what plays
@@ -345,17 +345,19 @@ def test_hero_is_none_when_nothing_fits(db):
     user, ch = _seed_yt(db)
     db.execute(text("DELETE FROM videos WHERE id = 'vlong'"))
     db.commit()
-    assert hero.pick(db, user, "long", seed=1) is None
+    assert hero.pick(db, user, "long", seed=1, lang="en") is None
 
 
 def test_surprise_is_reproducible_for_a_seed(db):
     """The reroll button depends on this: one seed drives both sources, so the same seed must give
     the same answer and a different seed must be free to give another."""
     user, _ = _seed_yt(db)
-    a = rails.surprise(db, user, "any", seed=7, limit=3)
-    b = rails.surprise(db, user, "any", seed=7, limit=3)
+    a = rails.surprise(db, user, "any", seed=7, limit=3, lang="en")
+    b = rails.surprise(db, user, "any", seed=7, limit=3, lang="en")
     assert [c["id"] for c in a] == [c["id"] for c in b]
-    seeds = {tuple(c["id"] for c in rails.surprise(db, user, "any", s, 3)) for s in range(12)}
+    seeds = {
+        tuple(c["id"] for c in rails.surprise(db, user, "any", s, 3, lang="en")) for s in range(12)
+    }
     assert len(seeds) > 1  # the seed actually reaches the ordering
 
 
@@ -374,7 +376,9 @@ def test_surprise_never_offers_something_already_started(db):
         )
     )
     db.commit()
-    assert "vlong" not in {c["id"] for c in rails.surprise(db, user, "long", seed=3, limit=5)}
+    assert "vlong" not in {
+        c["id"] for c in rails.surprise(db, user, "long", seed=3, limit=5, lang="en")
+    }
 
 
 def test_the_seed_decides_which_source_leads(db):
@@ -384,7 +388,9 @@ def test_the_seed_decides_which_source_leads(db):
     user, _ = _seed_yt(db)
     _seed_plex(db, user)
     _enable_plex(db)
-    leaders = {rails.surprise(db, user, "any", s, limit=1)[0]["source"] for s in range(6)}
+    leaders = {
+        rails.surprise(db, user, "any", s, limit=1, lang="en")[0]["source"] for s in range(6)
+    }
     assert leaders == {"youtube", "plex"}
 
 
@@ -413,10 +419,10 @@ def test_the_reroll_must_be_able_to_move_past_the_resume_tier(db):
     )
     db.commit()
 
-    first = hero.pick(db, user, "any", seed=1)
+    first = hero.pick(db, user, "any", seed=1, lang="en")
     assert first["card"]["id"] == "vmed"
     # Same seed, same everything — only the exclusion differs.
-    second = hero.pick(db, user, "any", seed=1, exclude={"youtube:vmed"})
+    second = hero.pick(db, user, "any", seed=1, exclude={"youtube:vmed"}, lang="en")
     assert second["card"]["id"] == "vshort"
 
 
@@ -438,7 +444,7 @@ def test_the_reroll_rotates_which_tier_answers(db):
     )
     db.add(ComfortPin(user_id=user.id, video_id="vlong", position=0))
     db.commit()
-    tiers = [hero.pick(db, user, "any", seed=1, start=n)["tier"] for n in range(4)]
+    tiers = [hero.pick(db, user, "any", seed=1, start=n, lang="en")["tier"] for n in range(4)]
     assert tiers == ["resume", "comfort", "surprise", "resume"]
 
 
@@ -447,7 +453,7 @@ def test_the_rotation_still_falls_through_an_empty_tier(db):
     Here there is no shelf at all, so the comfort-led press has to answer from somewhere else."""
     user, _ = _seed_yt(db)
     assert db.execute(select(func.count()).select_from(ComfortPin)).scalar_one() == 0
-    got = hero.pick(db, user, "any", seed=1, start=1)
+    got = hero.pick(db, user, "any", seed=1, start=1, lang="en")
     assert got is not None and got["tier"] != "comfort"
 
 
@@ -468,10 +474,10 @@ def test_excluding_a_show_also_excludes_the_episode_it_resolves_to(db):
     )
     db.commit()
 
-    shown = hero.pick(db, user, "any", seed=1)
+    shown = hero.pick(db, user, "any", seed=1, lang="en")
     assert shown["card"]["id"] == "ps1e1"  # the show resolved to its in-progress episode
     # Excluding what the USER saw — the show — must move the tier on, not return the episode again.
-    after = hero.pick(db, user, "any", seed=1, exclude={"plex:ps1"})
+    after = hero.pick(db, user, "any", seed=1, exclude={"plex:ps1"}, lang="en")
     assert after is None or after["card"]["id"] != "ps1e1"
 
 
@@ -518,7 +524,7 @@ def test_shelf_resolves_a_channel_to_its_newest_unwatched_video(db):
     user, ch = _seed_yt(db)
     db.add(ComfortPin(user_id=user.id, channel_id=ch.id, position=0))
     db.commit()
-    (card,) = pins.shelf(db, user)
+    (card,) = pins.shelf(db, user, lang="en")
     assert card["kind"] == "channel"
     assert card["unwatched_count"] == 3
     assert card["next"]["id"] == "vshort"  # newest
@@ -538,7 +544,7 @@ def test_shelf_resolves_a_playlist_to_its_first_unwatched_item(db):
     db.add(VideoState(user_id=user.id, video_id="vshort", status="watched", watched_at=NOW))
     db.add(ComfortPin(user_id=user.id, playlist_id=pl.id, position=0))
     db.commit()
-    (card,) = pins.shelf(db, user)
+    (card,) = pins.shelf(db, user, lang="en")
     assert card["kind"] == "playlist"
     assert card["item_count"] == 2
     assert card["next"]["id"] == "vmed"
@@ -585,7 +591,7 @@ def test_the_shelf_resolves_each_channel_and_playlist_on_its_own_terms(db):
 
     got = [
         (c.get("unwatched_count", c.get("item_count")), (c["next"] or {}).get("id"))
-        for c in pins.shelf(db, user)
+        for c in pins.shelf(db, user, lang="en")
     ]
     assert got == [(3, "vshort"), (1, "vother"), (1, "vlong"), (0, None)]
 
@@ -601,14 +607,14 @@ def test_the_shelf_costs_the_same_queries_for_one_pin_or_many(db):
     db.add(ComfortPin(user_id=user.id, channel_id=ch.id, position=0))
     db.add(ComfortPin(user_id=user.id, playlist_id=lists[0].id, position=1))
     db.commit()
-    few = _count_statements(db, lambda: pins.shelf(db, user))
+    few = _count_statements(db, lambda: pins.shelf(db, user, lang="en"))
 
     for i, c in enumerate(extra):
         db.add(ComfortPin(user_id=user.id, channel_id=c.id, position=10 + i))
     for i, p in enumerate(lists[1:]):
         db.add(ComfortPin(user_id=user.id, playlist_id=p.id, position=20 + i))
     db.commit()
-    assert _count_statements(db, lambda: pins.shelf(db, user)) == few
+    assert _count_statements(db, lambda: pins.shelf(db, user, lang="en")) == few
 
 
 def test_a_pinned_video_survives_leaving_the_feed_scope(db):
@@ -619,7 +625,7 @@ def test_a_pinned_video_survives_leaving_the_feed_scope(db):
     db.commit()
     db.execute(delete(Subscription))
     db.commit()
-    (card,) = pins.shelf(db, user)
+    (card,) = pins.shelf(db, user, lang="en")
     assert card["id"] == "vmed"
     assert card["next"]["id"] == "vmed"
 
@@ -633,7 +639,9 @@ def test_the_plex_surprise_obeys_the_time_budget(db):
     _seed_plex(db, user)
     _enable_plex(db)
     drawn = lambda budget: {  # noqa: E731
-        (c["source"], c["id"]) for s in range(6) for c in rails.surprise(db, user, budget, s, 5)
+        (c["source"], c["id"])
+        for s in range(6)
+        for c in rails.surprise(db, user, budget, s, 5, lang="en")
     }
     assert ("plex", "pm1") not in drawn("short")
     # …and it IS offered where it fits, so this cannot pass by the rail being empty.
@@ -658,7 +666,9 @@ def test_the_plex_surprise_never_offers_something_already_started(db):
     )
     db.commit()
     drawn = {
-        (c["source"], c["id"]) for s in range(6) for c in rails.surprise(db, user, "long", s, 5)
+        (c["source"], c["id"])
+        for s in range(6)
+        for c in rails.surprise(db, user, "long", s, 5, lang="en")
     }
     assert ("plex", "pm1") not in drawn
 
@@ -682,7 +692,7 @@ def test_a_new_pin_lands_at_the_end_even_after_a_hole(db):
 
     db.add(ComfortPin(user_id=user.id, channel_id=ch.id, position=pins.next_position(db, user)))
     db.commit()
-    assert [c["kind"] for c in pins.shelf(db, user)] == ["video", "channel"]
+    assert [c["kind"] for c in pins.shelf(db, user, lang="en")] == ["video", "channel"]
     positions = (
         db.execute(select(ComfortPin.position).order_by(ComfortPin.position)).scalars().all()
     )
@@ -695,7 +705,7 @@ def test_a_self_playing_pin_does_not_reference_itself(db):
     user, _ = _seed_yt(db)
     db.add(ComfortPin(user_id=user.id, video_id="vmed", position=0))
     db.commit()
-    (card,) = pins.shelf(db, user)
+    (card,) = pins.shelf(db, user, lang="en")
     assert card["next"] is not card
     assert "next" not in card["next"]
 
@@ -718,7 +728,7 @@ def test_the_resume_rail_says_what_would_actually_play(db):
         )
     )
     db.commit()
-    rail = rails.continue_watching(db, user)
+    rail = rails.continue_watching(db, user, lang="en")
     tile = next(c for c in rail if c["kind"] == "show")
     assert tile["id"] == "ps1"  # still the show
     assert tile["next"]["kind"] == "episode"
@@ -762,7 +772,7 @@ def test_only_a_show_row_pays_for_a_resolution(db):
     )
     db.commit()
 
-    rail = rails.continue_watching(db, user)
+    rail = rails.continue_watching(db, user, lang="en")
     # A video, a movie and a show — one row of each kind that can appear here, so the assertion below
     # actually exercises both sides of the equality.
     assert {c["kind"] for c in rail} == {"video", "movie", "show"}
@@ -778,7 +788,7 @@ def test_next_episode_takes_an_episode_with_no_state_row_at_all(db):
     _, show, ep1 = _seed_plex(db, user)
     db.add(PlexState(user_id=user.id, item_id=ep1.id, status="watched", watched_at=NOW))
     db.commit()  # ep2 has NO PlexState row
-    assert queries.next_episode(db, user.id, show.id)["id"] == "ps1e2"
+    assert queries.next_episode(db, user.id, show.id, lang="en")["id"] == "ps1e2"
 
 
 def test_a_finished_show_starts_again_from_the_top(db):
@@ -793,7 +803,7 @@ def test_a_finished_show_starts_again_from_the_top(db):
         ]
     )
     db.commit()
-    assert queries.next_episode(db, user.id, show.id)["id"] == "ps1e1"
+    assert queries.next_episode(db, user.id, show.id, lang="en")["id"] == "ps1e1"
 
 
 def test_next_episode_agrees_with_the_show_page_when_two_are_in_progress(db):
@@ -825,12 +835,16 @@ def test_next_episode_agrees_with_the_show_page_when_two_are_in_progress(db):
     )
     db.commit()
 
-    got = queries.next_episode(db, user.id, show.id)
+    got = queries.next_episode(db, user.id, show.id, lang="en")
     assert got["id"] == "ps1e2"
     # Asserted against the other implementation rather than against a literal, so the two cannot
     # drift apart again without this failing.
     ordered = [
-        leaf_card(ep, db.execute(select(PlexState).where(PlexState.item_id == ep.id)).scalar_one())
+        leaf_card(
+            ep,
+            db.execute(select(PlexState).where(PlexState.item_id == ep.id)).scalar_one(),
+            lang="en",
+        )
         for ep in (ep1, ep2)
     ]
     assert rollup.rollup(ordered)["resume"]["id"] == got["id"]
@@ -848,7 +862,7 @@ def test_next_episode_prefers_the_one_in_progress(db):
         ]
     )
     db.commit()
-    assert queries.next_episode(db, user.id, show.id)["id"] == "ps1e2"
+    assert queries.next_episode(db, user.id, show.id, lang="en")["id"] == "ps1e2"
 
 
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