fix: resolve intermittent stream closure failures in EventConsumer

[kabir]

Fixes two separate race conditions causing intermittent test failures:

1. Grace period closing streams before final events arrive

   • EventConsumer now checks awaitingFinalEvent flag before starting timeout counter, preventing premature closure when final events are in-transit through MainEventBusProcessor
   • Increased grace period timeout to 150ms for CI environment latency

2. Client auto-close IOException not filtered in testAuthRequiredWorkflow

   • AbstractSSEEventListener cancels SSE streams on final events (by design)
   • This generates "Stream cancelled" IOException that must be filtered
   • testAuthRequiredWorkflow was the only test missing this filter

[gemini-code-assist]

Code Review

This pull request implements a timeout mechanism for final events in the EventConsumer to prevent potential infinite polling. It introduces a maximum wait period (3 seconds) and increases the SSE buffer flush delay to 150ms to improve reliability in CI environments. Review feedback suggests refactoring the clearAwaitingFinalEvent logic into the EventQueue base class to avoid brittle type checking and identifies redundant flag-clearing logic in the ChildQueue dequeue process that should be removed.