fix(01-review): WR-01+WR-02 stable capture error codes + pure assertCodecSupported

tests/offscreen/codec-check.test.ts

@@ -17,14 +17,23 @@ describe('codec strict mode', () => {
     };
   });
 
-  it('throws on unsupported vp9 and emits RECORDING_ERROR', async () => {
+  // WR-02 fix: assertCodecSupported is a pure predicate that throws.
+  // The previous spec expected a RECORDING_ERROR broadcast from inside
+  // the assertion; that side-effect was removed (single-responsibility +
+  // it double-emitted with startRecording's catch block). The notify is
+  // now solely the caller's (startRecording's) responsibility — exercised
+  // via integration through `classifyCaptureError` rather than from this
+  // unit test, since `startRecording` requires a full getDisplayMedia
+  // stub that jsdom does not provide.
+  it('throws on unsupported vp9 (pure assertion, no side-effect)', async () => {
     (globalThis as unknown as GlobalWithChrome).MediaRecorder = {
       isTypeSupported: vi.fn().mockReturnValue(false),
     };
     const mod = await import('../../src/offscreen/recorder');
     expect(() => mod.assertCodecSupported()).toThrow(/vp9 unsupported/);
     const stub = (globalThis as unknown as GlobalWithChrome).chrome!;
-    expect(stub.runtime.sendMessage).toHaveBeenCalledWith(
+    // The assertion itself MUST NOT emit RECORDING_ERROR.
+    expect(stub.runtime.sendMessage).not.toHaveBeenCalledWith(
       expect.objectContaining({ type: 'RECORDING_ERROR' })
     );
   });
@@ -41,3 +50,74 @@ describe('codec strict mode', () => {
     );
   });
 });
+
+// WR-01 fix: classifyCaptureError maps DOMException / Error shapes to a
+// stable string union. The popup / SW route can switch on the code
+// instead of substring-matching DOMException.message — message text
+// changes between Chrome versions and locales, name and prototype do not.
+describe('classifyCaptureError (WR-01 stable error codes)', () => {
+  beforeEach(() => {
+    vi.resetModules();
+    (globalThis as unknown as GlobalWithChrome).chrome = {
+      runtime: { sendMessage: vi.fn() },
+    };
+    (globalThis as unknown as GlobalWithChrome).MediaRecorder = {
+      isTypeSupported: vi.fn().mockReturnValue(true),
+    };
+  });
+
+  function makeDomError(name: string, message: string): Error {
+    const e = new Error(message);
+    (e as { name: string }).name = name;
+    return e;
+  }
+
+  it('codec error → "codec-unsupported"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(new Error('vp9 unsupported. UA=<test>'))).toBe(
+      'codec-unsupported',
+    );
+  });
+
+  it('NotAllowedError (no system hint) → "user-cancelled"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(
+      mod.classifyCaptureError(makeDomError('NotAllowedError', 'Permission denied by user')),
+    ).toBe('user-cancelled');
+  });
+
+  it('NotAllowedError with "system" in message → "permission-denied"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(
+      mod.classifyCaptureError(makeDomError('NotAllowedError', 'Permission denied by system')),
+    ).toBe('permission-denied');
+  });
+
+  it('SecurityError → "permission-denied"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(makeDomError('SecurityError', 'blocked'))).toBe(
+      'permission-denied',
+    );
+  });
+
+  it('NotFoundError → "no-source-selected"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(makeDomError('NotFoundError', 'no source'))).toBe(
+      'no-source-selected',
+    );
+  });
+
+  it('AbortError → "capture-failed"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(makeDomError('AbortError', 'aborted'))).toBe(
+      'capture-failed',
+    );
+  });
+
+  it('arbitrary error → "unknown"', async () => {
+    const mod = await import('../../src/offscreen/recorder');
+    expect(mod.classifyCaptureError(new Error('totally novel failure'))).toBe('unknown');
+    expect(mod.classifyCaptureError('a bare string')).toBe('unknown');
+    expect(mod.classifyCaptureError(null)).toBe('unknown');
+  });
+});