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/Home.dom.test.tsx

@@ -1,6 +1,6 @@
 // @vitest-environment jsdom
 //
-// E24 S2: the Home surface. Covers the four behaviours the browser round actually caught, each of
+// The Home surface. Covers the four behaviours the browser round actually caught, each of
 // which is invisible to tsc and to a render-only check:
 //   • the hero's kicker comes from the SERVER's tier, never from the card's shape;
 //   • the hero is not printed twice (once as the hero, once as the first resume tile);
@@ -308,7 +308,7 @@ describe("Home", () => {
     // through the disabled seed-0 query the chip click leaves behind. So the first reroll under a new
     // budget offered the old budget's card — while it loaded, and permanently once it failed, since
     // `retry: false` makes a failed pick terminal. Under a chip that promises ten minutes, that makes
-    // the page's one control meaningless (round 2).
+    // the page's one control meaningless.
     discover.mockResolvedValue({
       budget: "any",
       hero: { tier: "resume", card: ytCard("v1", "Hero v1") },
@@ -381,7 +381,7 @@ describe("Home", () => {
     // every mark-watched, bookmark, pin and shelf move on this page refetches it in the BACKGROUND —
     // so binding the button's `loading` to raw `isFetching` made it spin and, since a `loading`
     // `ui/Button` swallows its clicks, ignore presses after actions the user never associated with a
-    // reroll (round 2). A press is outstanding only while THIS key has no answer of its own.
+    // reroll. A press is outstanding only while THIS key has no answer of its own.
     const rerollBtn = () =>
       screen.getByText("home.hero.reroll").closest("button") as HTMLButtonElement;
     let resolvePick!: (v: unknown) => void;
@@ -419,7 +419,7 @@ describe("Home", () => {
   });
 
   it("a press that FAILED does not leave the button hostage to the next mutation", async () => {
-    // Round 3's correction to the case above. A key whose request failed never gets data of its own
+    // A later correction to the case above. A key whose request failed never gets data of its own
     // (`retry: false` makes it terminal), so a predicate reading `data === undefined` stayed true
     // forever and every later background refetch re-disabled the button — the same defect, one
     // branch over. `isFetched` remembers that the key settled, an error counting as settled.
@@ -437,7 +437,7 @@ describe("Home", () => {
     await waitFor(() => expect(discoverPick).toHaveBeenCalledTimes(1));
     // `waitFor`, not a fixed tick: react-query hands the rejection to the observer through
     // `notifyManager`'s own `setTimeout(0)`, registered AFTER any timer this test schedules, so
-    // "await one macrotask then assert" races it. Round 4 measured that race as an intermittent red.
+    // "await one macrotask then assert" races it. That race was measured as an intermittent red.
     failPick(new Error("boom"));
     await waitFor(() => expect(rerollBtn().getAttribute("aria-busy")).toBeNull()); // the failure releases the button
 
@@ -454,7 +454,7 @@ describe("Home", () => {
     // The tagged slot is authoritative for its own budget, including when what it holds is "no hero
     // at all". Under a `??` chain that read as "nothing remembered" and fell through to the loaded
     // payload, so a failed press resurrected the card the page had already excluded as seen and just
-    // said it had nothing beyond (round 3).
+    // said it had nothing beyond.
     discover.mockResolvedValue({
       budget: "short",
       hero: { tier: "resume", card: ytCard("v1", "Hero v1") },
@@ -543,7 +543,7 @@ describe("Home", () => {
     expect(screen.getByText("Hero v1")).toBeTruthy();
   });
 
-  // E24 S4. The palette's "Meglepetés" is pressed on ANOTHER page, so Home's lazy chunk is not
+  // The palette's "Meglepetés" is pressed on ANOTHER page, so Home's lazy chunk is not
   // mounted yet — the request has to WAIT as a token rather than fire into an empty room. And it
   // must be spent: a token that survived would make a later visit reroll on its own, which reads as
   // the page overruling the answer you came back for.
@@ -703,7 +703,7 @@ describe("Home", () => {
       comfort: [],
     });
     mount();
-    // Since E28 C1 the tile's ⓘ is its menu's "Media info" row, opened from the tile's "…".
+    // The tile's ⓘ is now its menu's "Media info" row, opened from the tile's "…".
     fireEvent.click((await screen.findAllByRole("button", { name: "card.menu.more" }))[0]!);
     const info = screen
       .getAllByRole("menuitem", { hidden: true })
@@ -782,7 +782,7 @@ describe("Home", () => {
   });
 });
 
-// E11 S4b, owner decision D4: the rails are one keyboard page — `j` walks a rail's cards and goes on
+// The owner's decision: the rails are one keyboard page — `j` walks a rail's cards and goes on
 // into the next rail, whichever order the page stacks them in.
 describe("Home · keyboard", () => {
   it("walks the rails with j, from one rail on into the next", async () => {
@@ -828,7 +828,7 @@ describe("Home · keyboard", () => {
   });
 });
 
-// E28 S3h (the owner, 2026-09-26/27): the hero stands in three quarters of a wide page with its text
+// The owner's call (2026-09-26/27): the hero stands in three quarters of a wide page with its text
 // centred beside the picture; one fact line, no repeated year, and prose only where there is some,
 // at a readable measure.
 describe("Home's hero text", () => {
@@ -883,7 +883,7 @@ describe("Home's hero text", () => {
   });
 });
 
-describe("Home · the reader's language (E30)", () => {
+describe("Home · the reader's language", () => {
   it("asks for the page in Hungarian, so a Plex card comes back with its Hungarian title", async () => {
     setLanguage("hu");
     try {