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.

frontend/src/components/plexDetailAside.tsx

@@ -8,9 +8,9 @@ import { Filterable, PrefToggle } from "./plexDetailUi";
 import { Button } from "./ui/Button";
 import { Pressable } from "./ui/Pressable";
 
-// The detail pages' second column (E31, the owner's pick "A"): the TMDB facts and key crew of a movie or
+// The detail pages' second column (the owner's pick "A"): the TMDB facts and key crew of a movie or
 // a show beside its description, inside the hero — as the person page sets its known-for rail beside
-// the bio (E30 S6) — and its keywords under the text. They used to sit under the hero (movie) or
+// the bio — and its keywords under the text. They used to sit under the hero (movie) or
 // nowhere at all (show), while the hero's text stopped at ~55% of the panel and left the rest empty. A
 // narrow hero stacks the column under the text. Each section is a per-user toggle (default ON), the same
 // three prefs on both pages (lib/plexDetail useDetailAside).
@@ -35,7 +35,7 @@ export function DetailAsideToggles({ aside }: { aside: DetailAsideState }) {
 // The hero's second column: the facts over the key crew — two lists, read down. Null when neither is
 // shown. The keywords are chips that filter, as the genres are, so they sit under the text instead
 // (DetailKeywords): all three in this column ran it to twice the text's height at 20 keywords and 12
-// crew, a hole under the text — the measured worst case (E31 S4c).
+// crew, a hole under the text — the measured worst case.
 export function DetailAside({
   facts,
   shown,
@@ -56,9 +56,9 @@ export function DetailAside({
   );
 }
 
-// The structured facts (E5 S5): release / runtime / cert / budget / revenue / studios / countries, from
+// The structured facts: release / runtime / cert / budget / revenue / studios / countries, from
 // the title's own fields + the persisted TMDB block. What filters the library is an edged chip, a plain
-// fact stays flat text (E28 S3h, the S3d1 rule).
+// fact stays flat text (edged = pressable, flat = just says).
 function FactsSection({ facts, onFilter }: { facts: DetailFacts; onFilter?: OnFilter }) {
   const { t, i18n } = useTranslation();
   const lang = i18n.language;
@@ -152,7 +152,7 @@ function FactsSection({ facts, onFilter }: { facts: DetailFacts; onFilter?: OnFi
   );
 }
 
-// TMDB keyword chips (E5 S5) — tap one to filter the library by that keyword. Under the hero's text.
+// TMDB keyword chips — tap one to filter the library by that keyword. Under the hero's text.
 export function DetailKeywords({
   keywords,
   onFilter,
@@ -182,12 +182,12 @@ export function DetailKeywords({
 }
 
 // The crew shows its first CREW_SHOWN names and a "Show N more" that opens the rest: the column beside the
-// text is the hero's tallest part, and twelve names ran it ~170px past the text (E31, the owner's call).
+// text is the hero's tallest part, and twelve names ran it ~170px past the text (the owner's call).
 // A list only a little longer than that shows whole: a toggle that hides one or two names saves no room.
 export const CREW_SHOWN = 6;
 const CREW_FOLD_OVER = CREW_SHOWN + 2;
 
-// The TMDB key crew (E5 S5) — Director / Writer / Producer / …, each opening their person page. It
+// The TMDB key crew — Director / Writer / Producer / …, each opening their person page. It
 // complements the hero's Director line (which comes from Plex directly).
 function CrewSection({
   crew,