feat(01-13): wave-3B — A5+A6+A7 GREEN + Bug B canonical regression rewind

Wave 3B lands the A5 (SAVE_ARCHIVE → zip on disk) and A7 (genuine
RECORDING_ERROR → ERR + recovery notification) assertions, completing
8/14 of the orchestrator's GREEN floor (A0+A1+A2+A3+A4+A5+A6+A7).
Bails at A8 (Wave 3C scope).

Changes per file:

  tests/uat/extension-page-harness.ts
    - assertA5: 11s settle (>= SEGMENT_DURATION_MS so first rotation
      lands a segment) + send SAVE_ARCHIVE + assert resp.success=true.
      Page-side only checks SW handler ack; host-side driver verifies
      disk-side outcome (zip presence + size floor).
    - assertA7: setupFreshRecording helper (A6 tears down; A7 needs
      REC state) → snapshot notif count → send RECORDING_ERROR with
      a non-Bug-B error code ('codec-unsupported') → 200ms settle →
      assert badge='ERR' + popup endsWith popup.html + notif delta=1
      + set-membership for 'mokosh-recovery-*' prefix.
    - setupFreshRecording: shared helper for A7 + future assertions
      that need a fresh REC state after a teardown.

  tests/uat/lib/harness-page-driver.ts
    - driveA5: page.evaluate(assertA5) THEN host-side fs polling for
      *.zip in handles.downloadsDir. The CDP Browser.setDownloadBehavior
      override renames the file to download.zip (data: URL filename
      gap), so we accept any *.zip suffix. Merges page-side check +
      host-side checks into a single AssertionRecord. Signature now
      takes downloadsDir as a second arg.
    - driveA7: standard page.evaluate wrapper (no host-side work).

  tests/uat/harness.test.ts
    - Wraps driveA5 in a closure that captures handles.downloadsDir.
    - Reordered: launchHarnessBrowser MUST run before driver list so
      the closure can read handles without a TDZ trap.

  tests/uat/lib/launch.ts
    - Victim page switched from about:blank to a file:// URL backed by
      a tmp HTML file in downloadsDir. About:blank breaks A5 because
      chrome.tabs.captureVisibleTab needs <all_urls> permission which
      matches http/https/file/ftp but NOT about: or data: URLs. The
      stub HTML satisfies <all_urls> + provides a real .url for the
      production saveArchive's chrome.tabs.query.

  src/test-hooks/offscreen-hooks.ts (test-only — tree-shaken from prod)
    - installFakeDisplayMedia: mintStream() helper called per
      fakeGetDisplayMedia invocation; each call mints a FRESH
      MediaStream from the persistent canvas. Real getDisplayMedia
      returns a new stream per call — fake now matches. Required for
      A7's setupFreshRecording where the previous recording's stream
      tracks were stopped by A6's onUserStoppedSharing teardown.
    - Added 33ms setInterval-driven drawFrame() alongside the
      existing requestAnimationFrame loop. RAF can throttle in
      headless Chrome on offscreen documents (page-visibility
      heuristics produce 0 fps), which yields zero-byte
      MediaRecorder segments that crash ts-ebml's VINT decode in
      webm-remux.extractFramesFromSegment with "Unrepresentable
      length: Infinity". The setInterval is redundant when RAF fires
      at full rate; it's a safety net for the headless-MV3 corner.

Bug B regression-catch demo (success_criteria #3 — MANDATORY per plan):

Step 1 — apply local regression patch (NOT committed):
  src/background/index.ts:792  setIdleMode() → setErrorMode()

Step 2 — npm run build:test && npm run test:uat RED snippet:

  A6 — BUG B canonical: user-stopped-sharing routes via setIdleMode: FAIL
    [PASS] SETUP: badge becomes REC after start
    [FAIL] A6.1: badge text is '' (NOT 'ERR') after user-stop
           expected: ""
           actual:   "ERR"
    [FAIL] A6.2: popup is '' (NOT manifest default) after user-stop
           expected: ""
           actual:   "chrome-extension://<id>/src/popup/index.html"
    [PASS] A6.3: NO recovery notification fired (count delta === 0)
    [PASS] A6.4: isRecording=false (via badge proxy)

  UAT harness: 6/14 assertions passed (bailed: A6 failed; see above)

Step 3 — revert local patch (git checkout -- src/background/index.ts).

Step 4 — npm run build:test && npm run test:uat GREEN snippet:

  A6 — BUG B canonical: user-stopped-sharing routes via setIdleMode: PASS
    [PASS] SETUP: badge becomes REC after start
    [PASS] A6.1: badge text is '' (NOT 'ERR') after user-stop
    [PASS] A6.2: popup is '' (NOT manifest default) after user-stop
    [PASS] A6.3: NO recovery notification fired (count delta === 0)
    [PASS] A6.4: isRecording=false (via badge proxy)

  UAT harness: 8/14 assertions passed (bailed: A8 failed — NOT YET
  IMPLEMENTED — Wave 3C wires driveA8)

The harness CORRECTLY catches the Bug B regression — the canonical
debug 01-09-recovery-flow scenario (operator-initiated stop routed
through setErrorMode locks the operator out of restart because popup
stays pinned to SAVE-only mode). Bug B is now CI-callable end-to-end.

vitest 93/93 GREEN throughout (unit-test layer unaffected). Tier-1
grep gate GREEN (9 forbidden hook strings: 0 occurrences in dist/).
npm run build exit 0; npx tsc --noEmit exit 0.

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

tests/uat/harness.test.ts

@@ -8,13 +8,15 @@
 // Wave 3A scope — wires A0+A1+A2+A3+A4+A6 (A6 via the proven Wave-2
 // driver). A5+A7..A13 throw `NOT YET IMPLEMENTED — Wave 3<X> wires this`
 // from `tests/uat/lib/harness-page-driver.ts`; the bail-on-first-failure
-// loop stops at the first such throw. Expected Wave-3A diagnostic:
-//   "UAT harness: 5/14 assertions passed (A0+A1+A2+A3+A4 GREEN; bail at A5)"
-// A6 PASSES via the standalone `npx tsx tests/uat/a6.test.ts` entry —
-// the orchestrator-level A6 won't reach in Wave 3A because the
-// sequential loop bails at A5; A6 lands in the loop output once Wave 3B
-// implements driveA5. The orchestrator structure is final from Wave 3A
-// onward; future waves only fill in the assertion-driver stubs.
+// loop stops at the first such throw.
+//
+// Wave 3B (this file's current state) wires A5 (SAVE_ARCHIVE → zip on
+// disk) + A7 (genuine RECORDING_ERROR → ERR + recovery notification).
+// Expected diagnostic: "8/14 GREEN: A0+A1+A2+A3+A4+A5+A6+A7; bail at A8".
+// Wave 3C will wire A8+A9+A10; Wave 3D wires A11+A12+A13 for 14/14 GREEN.
+//
+// The orchestrator structure is final from Wave 3A onward; future waves
+// only fill in the assertion-driver stubs.
 //
 // Architectural commitments (per 01-11-SUMMARY.md, DO NOT REGRESS):
 //   - Single browser, single recording per run (state machine: idle →
@@ -245,11 +247,27 @@ async function main(): Promise<number> {
   // recording), then dispatch-ended. After A6 the recording is torn
   // down — A7+ would need to re-start or test post-stop state.
   //
-  // Wave 3A only A1..A4 wire to real impls; A5..A13 throw NOT YET
-  // IMPLEMENTED. Bail-on-first-failure stops the loop at A5 — A6's
-  // driver wires (via Wave 2's driveA6) but won't reach in this run.
+  // Wave 3B wires A5 + A7 in addition to A1..A4 + A6 — bail-on-first-
+  // failure stops at A8 (Wave 3C wires that). Expected diagnostic:
+  // "8/14 GREEN: A0+A1+A2+A3+A4+A5+A6+A7; A8..A13 NOT YET IMPLEMENTED".
   // The standalone `npx tsx tests/uat/a6.test.ts` entry remains the
-  // way to verify A6 in isolation during Wave 3A.
+  // way to verify A6 in isolation for inner-loop iteration.
+  process.stdout.write('Launching Chrome + opening harness page...\n');
+  const handles = await launchHarnessBrowser();
+  process.stdout.write(`Extension id: ${handles.extensionId}\n`);
+  process.stdout.write(`Downloads dir: ${handles.downloadsDir}\n\n`);
+
+  // Adapter: driveA5 needs `downloadsDir` (host-side fs polling); driveA12 +
+  // driveA13 return `AssertionWithBytes`. We wrap each in a closure that
+  // hides those signature differences so the orchestrator's driver list
+  // is uniform `Page -> Promise<AssertionRecord>`. The byte-returning
+  // drivers' extra fields are out-of-scope for Wave 3B; Wave 3D will
+  // extend the orchestrator to surface them when A12/A13 land. The driver
+  // list is constructed AFTER `launchHarnessBrowser` returns so the
+  // closure can capture `handles.downloadsDir` without a TDZ trap.
+  const driveA5Wrapped: (page: import('puppeteer').Page) => Promise<AssertionRecord> =
+    (page) => driveA5(page, handles.downloadsDir);
+
   const drivers: ReadonlyArray<{
     readonly name: string;
     readonly drive: (page: import('puppeteer').Page) => Promise<AssertionRecord>;
@@ -258,7 +276,7 @@ async function main(): Promise<number> {
     { name: 'A2', drive: driveA2 },
     { name: 'A3', drive: driveA3 },
     { name: 'A4', drive: driveA4 },
-    { name: 'A5', drive: driveA5 as (page: import('puppeteer').Page) => Promise<AssertionRecord> },
+    { name: 'A5', drive: driveA5Wrapped },
     { name: 'A6', drive: driveA6 },
     { name: 'A7', drive: driveA7 },
     { name: 'A8', drive: driveA8 },
@@ -269,11 +287,6 @@ async function main(): Promise<number> {
     { name: 'A13', drive: driveA13 as (page: import('puppeteer').Page) => Promise<AssertionRecord> },
   ];
 
-  process.stdout.write('Launching Chrome + opening harness page...\n');
-  const handles = await launchHarnessBrowser();
-  process.stdout.write(`Extension id: ${handles.extensionId}\n`);
-  process.stdout.write(`Downloads dir: ${handles.downloadsDir}\n\n`);
-
   const buffers = { swConsole: handles.swConsole, offConsole: handles.offConsole };
   const results: Array<{ name: string; passed: boolean; error?: string }> = [];
   let bailReason: string | null = null;