Relates to #2639.

Follow-up to #2641 and feedback in #2660 (AGENTS.md).

Summary of Changes

1. tests/tools/emulation.test.ts:

   • Completely migrated off withMcpContext, removing all real-browser launches, serverHooks, and HTTP fixtures.
   • All tool handler test suites (geolocation, viewport, userAgent, extraHttpHeaders, colorScheme, network, cpu) now use createHandlerMocks() from tests/mocks.ts and verify page.emulate() is invoked with exact expected arguments.

2. tests/McpPage.test.ts:

   • Added unit test coverage for McpPage.emulate() using createMockPuppeteerPage():
     • Offline network throttling settings and network blocking guard.
     • Secondary DevTools session CPU throttling delegation.
     • Geolocation set/clear behavior.
     • Viewport set/clear with default parameter merging.
     • Extra HTTP headers set/clear behavior.

Verification

• npm run check-format: Passed (clean ESLint + Prettier)
• npm run build: Compiled with exit code 0
• node scripts/test.js tests/tools/emulation.test.ts: 50/50 tests passed
• node scripts/test.js tests/McpPage.test.ts: 32/32 tests passed