fix(@angular/build): flush perf timings from within the diagnostic worker

[arturovt]

When ParallelCompilation is used, diagnoseFiles() runs in a worker thread. The cumulative duration Map (populated by profileSync(..., cumulative=true) inside collectDiagnostics) lives in that worker's module memory — the main thread's logCumulativeDurations() call never sees it, so timings were silently dropped.

Fix by owning the full reset→log cycle inside diagnoseFiles() itself, with a try/finally to guarantee the flush even if diagnostics throw.

Also adds unit tests covering call order, the empty-diagnostics path, result correctness, and the throw-still-flushes guarantee.

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Result:

[gemini-code-assist]

Code Review

This pull request introduces cumulative duration resetting and logging around the diagnostic collection phase in AngularCompilation.diagnoseFiles, along with a new test suite to verify this behavior. The review feedback points out a critical issue: running this lifecycle on the main thread (when parallel compilation is disabled) would prematurely clear and print cumulative timings. The reviewer suggests restricting this profiling lifecycle to worker threads by checking isMainThread from node:worker_threads via a helper method shouldFlushPerformanceTimings(), which can also be overridden in tests to maintain test coverage.

[alan-agius4]

Hi @arturovt, Thank you for catching this issue and putting together the initial fix. To keep the base AngularCompilation class clean and thread-agnostic, I’ve opened an alternative PR and use a unified timing aggregation approach.

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