fix: Preserve unrelated MCP server tool caches during invalidation - #1977

Summary

Invalidating docs can currently evict cached tools for an unrelated server named docs:extra when docs has no registered cache keys, including after a previous invalidation. Remove the fallback prefix scan so invalidation uses registered keys or the exact server name.

Add regression coverage for never-cached and repeatedly invalidated server names, confirm intended-server invalidation still works, and include an @openai/agents-core patch changeset.

Test plan

• Both new regression cases fail before the fix; all 70 MCP cache tests pass with it.
• All 7,374 tests across 240 files pass with pnpm test:review --maxWorkers=2; this profile excludes the repository's five optional Docker/local-process test files.
• Build, package/example type checks, generated declarations, lint, formatting, and changeset validation pass.
• Full CI test jobs pass on Node 22 and Node 24.3, including Node 22 published-package API checks; Windows sandbox checks also pass.
• Two independent review rounds completed with no blocking findings.
• Full local verification was attempted but remains incomplete: Docker sandbox tests fail because this environment cannot access the daemon or required bind paths, and the runner disconnected during broader verification. The full suites subsequently passed in CI on Node 22 and Node 24.3.

Issue number

Fixes #1976.

Checks

• Added regression tests
• Added a patch changeset
• Completed independent review before submission
• Ran the repository verification script
• Full Node 22 and Node 24.3 CI test jobs pass (local environment limitations above)