fix(plex): Restart only where an episode has a resume point; the Surprise draw is re-read, not redrawn

Show cards carry resumable (ShowState, from the same rollup) so a part-watched
show whose next episode is untouched offers Play, not a Continue and a Restart
that do the same thing; plexStarted is the one rule for cards and menus. The
Surprise rail's key sits under the discover root: whatever refreshes the rails
re-reads the draw (keep=) with its watch state now, kept past the 5-minute gc,
and only the reshuffle deals. Closing the player refreshes the Discover rails.
A show card's play acts on the last click only, and only where it was made.

backend/app/routes/plex/discover.py

@@ -23,7 +23,14 @@ from app.auth import current_user
 from app.db import get_db
 from app.models import PlexItem, PlexShow, PlexState, User
 from app.plex import rollup
-from app.plex.cards import display_title, leaf_card, movie_card, show_card
+from app.plex.cards import (
+    SHOW_NEW,
+    ShowState,
+    display_title,
+    leaf_card,
+    movie_card,
+    show_card,
+)
 from app.plex.query import (
     LibraryFilters,
     apply_meta_filters,
@@ -69,7 +76,7 @@ def _movie_cards(db: Session, uid: int, items: list[PlexItem], lang: str) -> lis
 
 def _show_cards(db: Session, uid: int, shows: list[PlexShow], lang: str) -> list[dict]:
     statuses = rollup.state_map(db, uid, [s.id for s in shows])
-    return [show_card(s, statuses.get(s.id, "new"), lang=lang) for s in shows]
+    return [show_card(s, statuses.get(s.id, SHOW_NEW), lang=lang) for s in shows]
 
 
 def _recently_added(
@@ -232,7 +239,9 @@ def _continue_watching(
         # `apply_show_state_filter` the grid uses, so the rail can't drift from the grid's definition.
         prog = rollup.agg_subquery(db, uid, include_resumed=True).subquery()
         sq = apply_show_state_filter(
-            select(PlexShow, prog.c.resumed_at).join(prog, prog.c.show_id == PlexShow.id),
+            select(PlexShow, prog.c.resumed_at, prog.c.inprog).join(
+                prog, prog.c.show_id == PlexShow.id
+            ),
             prog.c.total,
             prog.c.watched,
             prog.c.inprog,
@@ -243,8 +252,9 @@ def _continue_watching(
             .order_by(prog.c.resumed_at.desc().nullslast())
             .limit(RAIL_LIMIT)
         ).all()
-        for sh, resumed_at in srows:
-            rows.append((resumed_at, show_card(sh, "in_progress", lang=lang)))
+        for sh, resumed_at, inprog in srows:
+            state = ShowState("in_progress", (inprog or 0) > 0)
+            rows.append((resumed_at, show_card(sh, state, lang=lang)))
 
     rows.sort(key=lambda r: r[0] or rollup.NO_TS, reverse=True)
     return [card for _, card in rows[:RAIL_LIMIT]]
@@ -420,6 +430,43 @@ def _draw(db: Session, stmt, key_col, per: int, exclude: list[str]) -> list:
     return [*fresh, *rest.all()]
 
 
+def _kept(
+    db: Session, uid: int, movie_ids: list[int], show_ids: list[int], keep: list[str], lang: str
+) -> list[dict]:
+    """The `keep` titles' cards in their given order, as they stand now: a title watched since the draw
+    stays in it, marked watched, and one gone from the scope's libraries drops out."""
+    movies = (
+        db.execute(
+            select(PlexItem).where(
+                PlexItem.kind == "movie",
+                PlexItem.library_id.in_(movie_ids),
+                PlexItem.rating_key.in_(keep),
+            )
+        )
+        .scalars()
+        .all()
+        if movie_ids
+        else []
+    )
+    shows = (
+        db.execute(
+            select(PlexShow).where(PlexShow.library_id.in_(show_ids), PlexShow.rating_key.in_(keep))
+        )
+        .scalars()
+        .all()
+        if show_ids
+        else []
+    )
+    cards = {
+        c["id"]: c
+        for c in [
+            *_movie_cards(db, uid, list(movies), lang),
+            *_show_cards(db, uid, list(shows), lang),
+        ]
+    }
+    return [cards[k] for k in keep if k in cards]
+
+
 @router.get("/surprise")
 def surprise(
     scope: str = "both",
@@ -427,6 +474,9 @@ def surprise(
     limit: int = Query(default=2 * SURPRISE_PER_KIND, ge=1, le=40),
     # The previous draw's rating keys: a reshuffle deals other titles first.
     exclude: list[str] = Query(default=[], max_length=40),
+    # The draw on screen, read again rather than redrawn: its titles' watch state moves (a play, a
+    # toggle) while the draw itself stands until the ↻.
+    keep: list[str] = Query(default=[], max_length=40),
     f: LibraryFilters = Depends(),
     user: User = Depends(current_user),
     db: Session = Depends(get_db),
@@ -439,6 +489,8 @@ def surprise(
     lang = _norm_lang(lang)
     p = f.as_dict()
     movie_ids, show_ids = _scope_libs(db, scope)
+    if keep:
+        return {"scope": scope, "items": _kept(db, user.id, movie_ids, show_ids, keep, lang)}
     per = min(limit, SURPRISE_PER_KIND)
     movies = []
     if movie_ids: