test(stealth): comprehensive unit + e2e tests, fix platform mismatch

Tests (52 total, 0 failures):

Unit tests (33):
- Module exports validation (stealthArgs shape, applyStealthPatches type)
- Launch args content (AutomationControlled, no-first-run, no forbidden flags)
- Init script source analysis (all 10 patch vectors verified present)
- applyStealthPatches API (mock context, GPU args, serialization, idempotency)
- Adversarial edge cases (array spread safety, extension compat, GPU plausibility)
- Import integration (browser-manager.ts correctly imports and calls both paths)
- Old inline patches removal verification

E2E tests (19):
- Real Chromium launch with stealth patches applied
- navigator.webdriver value AND property existence
- WebGL1 + WebGL2 renderer spoofing
- PluginArray instanceof + shape verification
- Complete chrome object (app, runtime, loadTimes, csi)
- Languages, permissions, CDP artifacts, Playwright globals
- Platform/UA consistency
- Patches survive page navigation

Bug fix: navigator.platform now spoofed to 'MacIntel' when UA claims
Macintosh. Previously reported 'Linux x86_64' in containers, which
contradicts the Mac user agent and is a detectable fingerprint mismatch.
Caught by the e2e test.

browse/src/stealth.ts

@@ -188,7 +188,7 @@ export async function applyStealthPatches(
       }
 
       // ========================================
-      // 5. LANGUAGES
+      // 5. LANGUAGES + PLATFORM
       // ========================================
       Object.defineProperty(navigator, 'languages', {
         get: () => ['en-US', 'en'],
@@ -196,6 +196,16 @@ export async function applyStealthPatches(
         configurable: true,
       });
 
+      // Platform must match the user agent. If UA says Mac, platform must be MacIntel.
+      // navigator.platform is 'Linux x86_64' in containers which contradicts a Mac UA.
+      if (navigator.userAgent.includes('Macintosh')) {
+        Object.defineProperty(navigator, 'platform', {
+          get: () => 'MacIntel',
+          enumerable: true,
+          configurable: true,
+        });
+      }
+
       // ========================================
       // 6. CDP ARTIFACT CLEANUP
       // ========================================