chore(01-13): wave-0 — clean broken Approach-A artifacts per 01-11-SUMMARY

Restore a clean baseline before promoting the c647f61 prototype to
production paths (Wave 1) and building out Approach-B driver
scaffolding (Wave 2). All deletions trace back to falsifications
documented in 01-11-SUMMARY.md.

Deleted — broken Approach-A files:
  - src/test-hooks/sw-hooks.ts
      MV3 SW blocks dynamic import (Chromium es_modules.md;
      w3c/webextensions#212). The gated `await import('../test-hooks/
      sw-hooks')` from 01-11 Wave 1 never resolved → SW silently died →
      production listeners never registered. File was dead-on-arrival;
      no fix possible while MV3 SWs disallow dynamic import. Approach-B
      replaces SW-side instrumentation with the extension-internal
      harness page's chrome.action.* + chrome.notifications.* surface
      (full privilege; no monkey-patching needed).

  - tests/uat/lib/{launch,extension,sw,offscreen,assertions}.ts
      Popup-bridge architecture (01-11 dbd977c) — falsification 2 +
      falsification 3 in 01-11-SUMMARY: `sw.evaluate` exposes only
      chrome.{loadTimes,csi}, NOT chrome.action.* / chrome.notifications.*
      / chrome.runtime.sendMessage; setPopup-juggling for extension-id
      resolution turned out to be unnecessary (browser.extensions()
      works directly per the prototype). These files will be reborn in
      Wave 2 around the extension-page architecture.

      Kept: tests/uat/lib/zip.ts (host-side JSZip work — architecture-
      agnostic; A12+A13 still use it) and tests/uat/lib/test-hook-
      contract.d.ts (type mirror — extended in Wave 3 but kept as-is here).

  - tests/uat/prototype/probe_{offscreen,sw,tabs,tabs2}.mjs
      Feasibility-research probes (01-11 spike) that empirically falsified
      the Approach-A hypotheses. The findings are encoded in 01-11-
      SUMMARY.md; the probes themselves are dead code.

  - tests/uat/harness.test.ts
      01-11 Wave 2 popup-bridge orchestrator (dbd977c). Imports the
      now-deleted tests/uat/lib/{assertions,extension,sw,offscreen,launch}
      modules — would not typecheck after this commit. Reborn in
      Wave 3A as the Approach-B orchestrator (extension-internal page
      driver + A0 grep gate + 13 assertion drivers).

Reverted — SW-side dynamic-import gate comment block:
  - src/background/index.ts lines 13-29
      The existing comment block (post-spike) described the SW-side
      gated dynamic import that never landed. Rewritten to cite 01-13
      Approach-B explicitly, link to 01-11-SUMMARY.md falsification,
      and clarify that the Tier-1 grep gate's enduring value is
      catching regressions in the offscreen chunk's __MOKOSH_UAT__
      gate (the SW chunk is hook-free by construction).

Updated — Tier-1 grep gate FORBIDDEN_HOOK_STRINGS inventory:
  - tests/background/no-test-hooks-in-prod-bundle.test.ts
      Removed: `simulateUserStop` (Approach-A naming; replaced by
      Approach-B `dispatchEndedOnTrack` which matches the W3C
      dispatchEvent semantics per RESEARCH §7 BLOCKER — track.stop()
      does NOT fire 'ended' per spec, so the simulation MUST use
      dispatchEvent).
      Added: `installFakeDisplayMedia`, `uninstallFakeDisplayMedia`,
      `dispatchEndedOnTrack`, `__mokoshOffscreenQuery`.
      Total inventory: 8 surface strings (was 5). Each MUST be absent
      from every file under dist/ post-build.

Verification (all GREEN):
  - `npm run build` — exit 0; dist/ populated.
  - `grep -rln <forbidden> dist/` — 0 matches.
  - `npm run build:test` — exit 0; dist-test/ populated; offscreen-hooks
    chunk contains `installFakeDisplayMedia` (gate runs correctly
    against the test build's distinct artifact).
  - `npx tsc --noEmit` — exit 0 (root + tests/uat/tsconfig.json).
  - `npx vitest run` — 92/92 tests passing (was 89; the +3 new tests
    come from the FORBIDDEN_HOOK_STRINGS list expanding 5 → 8 — each
    forbidden string is one parametric `it(...)` block).

Both prior-failing tests now GREEN:
  - tests/background/sw-bundle-import.test.ts (was missing dist/ → 92/92
    requires the test run to have a current dist/; vitest gate test
    rebuilds via execFile when SKIP_BUILD≠1, otherwise relies on prior
    `npm run build`).
  - tests/background/no-test-hooks-in-prod-bundle.test.ts (was failing
    on stale dist; now GREEN against the freshly-rebuilt clean bundle).

Wave 1 (next): promote tests/uat/prototype/{extension-page-harness.html,
extension-page-harness.ts,a6.test.ts} to tests/uat/ via `git mv`;
update vite.test.config.ts rollup input.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/background/index.ts

@@ -10,22 +10,36 @@ import type {
 import { remuxSegments } from './webm-remux';
 import JSZip from 'jszip';
 
-// ─── Plan 01-11: gated test-hook dynamic import ───────────────────────
-// MUST run BEFORE any chrome.* addListener call below so the SW-side
-// test hook's addListener monkey-patches catch every handler
-// registration. The `__MOKOSH_UAT__` token is text-replaced by Vite at
-// build time — `false` in production (vite.config.ts), `true` only in
-// the test bundle (vite.test.config.ts). The `if (false)` branch is a
-// static dead branch and Rollup tree-shakes the entire `await import`
-// away (Plan 01-11 RESEARCH §6, refined: we use a dedicated token
-// rather than `import.meta.env.MODE === 'test'` because vitest also
-// runs with MODE='test' and gating on MODE would activate the hooks
-// inside unit tests + clobber their vi.fn() chrome.* mocks).
+// ─── Plan 01-13: NO SW-side test hook gate (Approach B) ──────────────
+// Plan 01-11 originally planned a gated `await import('../test-hooks/sw-hooks')`
+// here to instrument chrome.* handler registrations from the SW side.
+// EMPIRICAL FALSIFICATION (01-11 spike, see 01-11-SUMMARY.md): MV3
+// service workers BLOCK dynamic import (Chromium es_modules.md:
+// "Dynamic import is currently blocked in Service Workers, but it
+// will change in the future."; w3c/webextensions#212 still open as of
+// May 2026). The `await import(...)` never resolved → the SW silently
+// died at top-of-module init → production chrome.* listeners never
+// registered → the entire service worker was non-functional.
 //
-// The Tier-1 grep gate `tests/background/no-test-hooks-in-prod-bundle
-// .test.ts` enforces that `__mokoshTest` is absent from every file
-// under `dist/` post-build (T-1-11-01 — Elevation of Privilege via
-// leaked hook surface).
+// Plan 01-13 (Approach B) DROPS the SW-side hook entirely:
+//   - The OFFSCREEN-side test hook (src/test-hooks/offscreen-hooks.ts)
+//     still works because offscreen IS a DOM document where dynamic
+//     import is supported. See src/offscreen/recorder.ts top-of-module
+//     for the surviving `if (__MOKOSH_UAT__) { await import(...) }`.
+//   - SW-side state (badge text, popup, isRecording proxy) is queried
+//     by the extension-internal harness page via chrome.action.*
+//     directly (the page has full chrome.* privilege, unlike the
+//     restricted CDP `sw.evaluate` surface that 01-11 tried first).
+//   - Architectural rationale + full falsification table:
+//     .planning/phases/01-stabilize-video-pipeline/01-11-SUMMARY.md
+//
+// SECURITY INVARIANT (T-1-11-01, retained): production bundle MUST
+// contain NO test-hook surface strings. The Tier-1 grep gate
+// `tests/background/no-test-hooks-in-prod-bundle.test.ts` enforces
+// post-build. In Approach B this invariant is trivially satisfied for
+// the SW chunk (no hook imports here at all); the gate's enduring
+// value is catching regressions in the offscreen chunk's
+// `__MOKOSH_UAT__` gate.
 
 // Default MIME applied when a wire chunk somehow lacks a type
 // field (defense-in-depth: in normal operation the offscreen recorder