fix(message): bound trace request cache

[tju-yxq]

What changed

Message Explorer deduplicates trace lookups in a page-local Map, but successful promises were retained indefinitely. A long investigation session with many distinct messages could therefore keep every resolved trace response referenced until the page was destroyed.

This change replaces the unbounded map with a small LRU promise cache:

• cap retained trace requests at 32 entries;
• refresh recency when an existing trace is reopened;
• evict the least-recently-used entry when the cap is exceeded;
• keep in-flight request de-duplication unchanged;
• continue removing rejected requests so a failed lookup can be retried;
• add focused tests for capacity validation, LRU eviction, replacement, deletion, and cleanup.

The cache is page-local and does not alter trace query results or server-side history recording.

Closes #3297

Validation

• npm test -- boundedPromiseCache.test.ts --run — 4 tests passed
• npm test -- MessagePageAsyncState.test.tsx MessagePage.test.tsx --run — 27 tests passed
• npm run lint -- --quiet — 0 errors; 10 existing warnings remain elsewhere in the tree
• npm run build — passed
• git diff --check — passed

The GitHub Actions status is not being described as green here; the checks above are local validation on this branch.

[RockteMQ-AI]

Summary

This PR replaces the unbounded Map used for trace request caching with a well-implemented LRU cache (BoundedPromiseCache) capped at 32 entries. This prevents memory leaks during long investigation sessions where many distinct messages are explored.

Strengths:

• Clean LRU implementation using Map insertion order
• Proper recency refresh on get() (delete + re-set)
• Good test coverage: capacity validation, eviction, replacement, deletion, cleanup
• Correct handling of rejected promises (removed from cache to allow retry)
• Proper input validation (maxEntries must be positive integer)

No blocking issues found. The implementation is solid and follows best practices.

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