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/lib/api/admin.ts

@@ -55,7 +55,7 @@ export interface ConfigItem {
 }
 export interface SystemConfigData {
   groups: Record<string, ConfigItem[]>;
-  /** The page's headings, in order, each with its groups in order; every group is in one (E31). */
+  /** The page's headings, in order, each with its groups in order; every group is in one. */
   sections: { id: string; groups: string[] }[];
   secrets_manageable: boolean;
 }
@@ -74,14 +74,14 @@ export interface AdminUserRow {
    *  account) from "we took it away" — different problems needing different help. */
   password_revoked_at: string | null;
   has_google: boolean;
-  /** The Google account's address, ONLY when it differs from the account address (E9.5 S3). */
+  /** The Google account's address, ONLY when it differs from the account address. */
   google_email: string | null;
   created_at: string | null;
   /** Last sign-in (Google or password). Null = not since 0.88 (no backfill). */
   last_login_at: string | null;
 }
 
-/** The account panel's view of why someone can or cannot get in (E12 S5). */
+/** The account panel's view of why someone can or cannot get in. */
 export interface AdminUserAccess extends AdminUserRow {
   /** The address passes the invite gate — so Google sign-in will be let through, not filed as a
    *  fresh access request. */
@@ -193,7 +193,7 @@ export interface SchedulerJob {
   last_started: string | null;
   last_finished: string | null;
   last_result: string | null; // the English one-liner — the fallback for a job with no `result`
-  // The last result as data (E30): counts, a `skipped` / `reason` word, a nested dict per phase —
+  // The last result as data: counts, a `skipped` / `reason` word, a nested dict per phase —
   // named in the reader's language by lib/jobResult.
   result: JobResult | null;
   last_error: string | null;
@@ -241,7 +241,7 @@ export const adminApi = {
     req(`/api/admin/config/${key}`, { method: "DELETE" }),
   testEmail: (): Promise<{ sent: boolean; to: string }> =>
     req("/api/admin/config/test-email", { method: "POST" }),
-  /** The bug-report tracker (E16): answers, takes issues, and is private. */
+  /** The bug-report tracker: answers, takes issues, and is private. */
   testIssues: (): Promise<{ ok: true; repo: string; url: string | null }> =>
     req("/api/admin/config/test-issues", { method: "POST" }),
   // --- users & roles ---