chore(comments): drop epic, sprint and review-round ids from the code

The code cited its plan instead of saying why: `E28 review J4`, `(R6 S3b)`, `S1 justified…`,
`deep-review round 5`. That plan lives in the private ops repo, so for every reader of this one the
citation was noise, and a sentence whose subject was the plan step ("round 2 showed…") hid its
lesson behind an id. Each one is gone and the "why" kept: a bare citation is deleted, a sentence
carrying a lesson is reworded around it ("a later attempt showed…").

Measured (`scripts/audit_metrics.py`, product code): 652 lines in 270 files carried an epic code by
the definition the next commit holds (507 / 241 by the old, two-digit-only one) -> 0. Across all
code, tests, scripts and configs: ~1100 epic-code lines plus ~320 sprint/round ids.

Behaviour unchanged, checked mechanically: every changed .py file has the same AST once docstrings
are blanked; css/sh/toml/yml/json files are identical once comments are stripped; the only
non-comment changes in TS/JS are test titles, one description string in a contract table, and five
ESLint messages, whose text is all the gates snapshot diff holds. Not touched: Markdown (docs and
the changelog keep their history), Alembic migrations, TV episode notation (`S2 · E5`), DESIGN.md
ids (`C1`, `B4`, `S3h`), tracker ids (`SEC-16`, `DX-17`).

One stale claim fixed on the way: test_hls_reaper's docstring said the player checkpoints "every
10 s whether or not it is playing", which plex/stream.py calls wrong; it now says what the code does.

backend/tests/test_not_found_detail.py

@@ -1,4 +1,4 @@
-"""A row that is gone answers with a reason the bilingual UI can translate (deep-review round 3).
+"""A row that is gone answers with a reason the bilingual UI can translate.
 
 The 404 a user actually meets is the one for something deleted in another tab or on another device.
 `owned_or_404` / `get_or_404` sent it as a bare English string ("Unknown view", "Not found"), and the
@@ -24,8 +24,8 @@ def test_a_gone_view_tag_or_pin_says_what_is_gone(db, make_user, as_user):
 
 
 def test_a_gone_channel_video_or_user_says_what_is_gone(db, make_user, as_user):
-    """The siblings that still hand-wrote `db.get(...) is None → 404 "Unknown …"` (deep-review
-    round 4): the same gone row, but the Hungarian UI showed the English."""
+    """The siblings that still hand-wrote `db.get(...) is None → 404 "Unknown …"`: the same
+    gone row, but the Hungarian UI showed the English."""
     admin = make_user(role="admin")
     client = as_user(admin)
     for method, url, body, what in [
@@ -45,12 +45,12 @@ def test_a_gone_channel_video_or_user_says_what_is_gone(db, make_user, as_user):
 
 
 def test_every_gone_channel_route_says_it_the_same_way(db, make_user, as_user, override_dep):
-    """The round-4 sweep converted ONE of the five `db.get(Channel, …) is None -> 404 "Unknown
+    """An earlier sweep converted ONE of the five `db.get(Channel, …) is None -> 404 "Unknown
     channel"` sites (block), and shipped the HU/EN string with it — so the Hungarian UI said it in
-    Hungarian on the Block button and in English on the four beside it (deep-review round 5). The
+    Hungarian on the Block button and in English on the four beside it. The
     asymmetric fix is the smell this repo bans, so all five are pinned together.
 
-    Literally all five: round 6 found this loop issuing three requests under a docstring claiming
+    Literally all five: a review found this loop issuing three requests under a docstring claiming
     five, with explore silently absent and subscribe excused as "covered by the tags route" — which
     reaches `_user_subscription`, a different site answering `reason: subscription`. Reverting
     either of those two to its bare English string left the whole lane green."""
@@ -77,7 +77,7 @@ def test_a_gone_subscription_recipient_or_job_says_what_is_gone(db, make_user, a
     verbatim into an otherwise Hungarian UI: "Not subscribed to this channel", "No user with that
     email.", "Unknown job".
 
-    All three, with a request each. Round 6 found this test naming three and issuing two: the
+    All three, with a request each. A review found this test naming three and issuing two: the
     recipient site had no test in the whole suite (nor did the `errors.notFound.recipient` keys
     added beside it), and `run_job_now` rode on its PATCH sibling's coverage."""
     admin = make_user(role="admin")
@@ -117,8 +117,8 @@ def test_a_gone_subscription_recipient_or_job_says_what_is_gone(db, make_user, a
 
 def test_a_nul_in_a_request_string_is_a_422_not_a_500(db, make_user, as_user):
     """Postgres cannot hold NUL in text, so the driver refuses the query outright: a DataError, i.e.
-    a 500 with a traceback, wherever a `%00` or an escaped NUL reached a comparison (deep-review
-    round 4 — round 3 had guarded only the by-rating_key lookup). One app-wide handler now answers
+    a 500 with a traceback, wherever a `%00` or an escaped NUL reached a comparison (an
+    earlier fix had guarded only the by-rating_key lookup). One app-wide handler now answers
     all of them."""
     client = as_user(make_user())
     r = client.get("/api/plex/playlists?contains=%00")
@@ -132,7 +132,7 @@ def test_any_other_data_error_is_still_a_500():
     registered for EVERY DataError on every route and decides on a substring of the driver's message,
     so only a NUL may become a 422. Without this, simplifying it to an unconditional 422 — it reads
     like dead defensive code — would answer a numeric overflow or an over-long ingested title with
-    "your input was bad", losing the traceback that names the real fault (deep-review round 5)."""
+    "your input was bad", losing the traceback that names the real fault."""
     import asyncio
 
     import pytest