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/auditColumns.dom.test.tsx

@@ -1,6 +1,6 @@
 // @vitest-environment jsdom
 //
-// E30: an audit row whose server summary is a fixed English line ("rss_poll: ok — new=5, failed=0",
+// An audit row whose server summary is a fixed English line ("rss_poll: ok — new=5, failed=0",
 // "log_level = DEBUG", "Background sync paused") reads in the reader's language, rebuilt from the row's
 // data through the REAL catalog. A row whose summary is data (an e-mail, a URL) keeps it.
 import { afterEach, describe, expect, it } from "vitest";
@@ -10,7 +10,7 @@ import type { AuditRow } from "../lib/api";
 import { auditColumns } from "./auditColumns";
 
 // Unmount BEFORE the language goes back: a mounted reader re-renders on the switch, and under a loaded
-// run that render landed after the test environment was gone ("window is not defined", E31 S5).
+// run that render landed after the test environment was gone ("window is not defined").
 afterEach(() => {
   cleanup();
   setLanguage("en");
@@ -87,7 +87,7 @@ describe("an audit row's details", () => {
     expect(details(secret)).toMatch(/ \| titok frissítve/);
   });
 
-  it("name a nested result and a skipped run from the row's data (E30 review)", () => {
+  it("name a nested result and a skipped run from the row's data", () => {
     const nested = row({
       target_type: "job",
       target_id: "people_enrich",
@@ -158,7 +158,7 @@ describe("an audit row's details", () => {
   });
 });
 
-// E31: a folded run (lib/auditGroups) shows its newest run and opens to the earlier ones; a failed run
+// A folded run (lib/auditGroups) shows its newest run and opens to the earlier ones; a failed run
 // is the line to see in a page of routine ones.
 describe("a folded run of one job", () => {
   const ok = (id: number, enriched: number) =>