feat(T2.2): implement parallel task dispatcher
- Add internal/dispatch package for concurrent task execution
- Implement Task interface for flexible task types
- Implement Dispatcher with configurable max concurrency
- Semaphore-based concurrency control for thread safety
- Parallel execution of multiple tasks with context support
- Task result aggregation with timing metrics
- Speedup calculation: sum of task durations / wallclock time
- Per-task timing: start time, end time, duration
- Completion tracking and status queries
- Statistics collection (total, completed, duration metrics)
- 15 dispatch tests, all passing
Features:
- DispatchAll() for concurrent task execution
- Configurable concurrency limit (default 10, semaphore-based)
- Error handling without blocking other tasks
- Wall-clock execution time measurement
- Task duration aggregation
- Speedup metrics (parallel efficiency)
- Context cancellation support
- MockTask helper for testing
Verification:
- 9 tasks @ 100ms each run in ~100ms (speedup ~9x) ✓
- Concurrency limit enforced ✓
- All tasks complete even with errors ✓
- Timing metrics accurate ✓
- Speedup calculation correct ✓
Performance:
- Linear speedup with task count
- Minimal overhead from dispatching
- Thread-safe concurrent execution
- Configurable parallelism
Next: T2.3 (Prompt template caching)
Test
b77c7b5f56