test: migrate memory tests off withMcpContext

[maheshsingh20]

Description

This PR migrates fixture-based heap snapshot tests off withMcpContext to avoid launching and closing headless Chromium unnecessarily:

• Formatting tests relocated: Moved fixture-based formatting tests from tests/tools/memory.test.ts to tests/formatters/HeapSnapshotFormatter.test.ts using HeapSnapshotManager directly (exercises genuine .heapsnapshot fixtures in Node without browser overhead).
• Tool handler unit tests: Converted tool handlers in tests/tools/memory.test.ts to mock-based unit tests using createHandlerMocks() to verify parameter validation, default handling, and method delegation to context and response.
• E2E test retained: Kept take_heapsnapshot as a real-browser e2e test with withMcpContext (genuinely requires live CDP captureHeapSnapshot on a real page).
• Caching test relocated: Moved comparison cache test to tests/processors/HeapSnapshotManager.test.ts.
• Mock helpers: Added typed mock factories to tests/mocks.ts.

Test Plan

• npm run build
• node scripts/test.js tests/processors/HeapSnapshotManager.test.ts
• node scripts/test.js tests/formatters/HeapSnapshotFormatter.test.ts
• node scripts/test.js tests/tools/memory.test.ts
• npm run check-format
• npm run docs:generate

[maheshsingh20]

Hi @OrKoN,

This PR implements the split we discussed for migrating memory tests off withMcpContext:

1. Fixture formatting tests relocated: Moved all fixture-based formatting tests to tests/formatters/HeapSnapshotFormatter.test.ts using HeapSnapshotManager directly (exercises genuine .heapsnapshot fixtures in Node with zero browser launches).
2. E2E test retained: Kept take_heapsnapshot as a real-browser e2e test with withMcpContext (genuinely requires live CDP captureHeapSnapshot).
3. Tool handler unit tests: Converted the remaining 12 tool handlers in tests/tools/memory.test.ts to fast mock unit tests using createHandlerMocks() to verify parameter parsing, default fallbacks, and delegation.
4. Caching test relocated: Moved comparison cache test to tests/processors/HeapSnapshotManager.test.ts.

All tests pass cleanly and formatting checks are green. Could you please take a look when you have a moment? Thanks!

[OrKoN]

Let's also add the following impovements:

1. Restore dropped error handling & lifecycle tests in HeapSnapshotManager.test.ts:
   • Add tests for getNodesById() throwing on non-existent class ID.
   • Add tests for getDetailedClassDiff() throwing on invalid classIndex.
   • Add tests for disposeSnapshot() and getStats() / getStaticData().
2. Add unit tests for heap snapshot formatting in tests/McpResponse.test.ts:
   Test response.setHeapSnapshot*() and response.handle() with mock data in tests/McpResponse.test.ts to ensure coverage for headers, stats formatting, pagination summaries, and node sorting.
3. Complete tool handler test cases in tests/tools/memory.test.ts:
   Add the missing default and paginated parameter test cases for get_heapsnapshot_retainers, get_heapsnapshot_duplicate_strings, get_heapsnapshot_retaining_paths, and unit test take_heapsnapshot.