Bug fixes:
- Fix eventfd error handling: return actual syscall error instead of nil
- Fix rawRead/rawWrite return value handling on error (-1 case)
- Fix timer initialization: stop immediately after creation to avoid spurious timeout
- Fix timeout heap cleanup: properly remove entries in deliver()

Performance optimizations:
- Pre-allocate maps (descs, connIdents) with initial capacity for C10K scenarios
- Pre-allocate slices (pendingCreate, pendingProcessing, recycles, eventSet)
- Add fdDescPool to reuse fdDesc objects and reduce allocations
- Optimize handleEvents: use index-based loop and early length check
- Optimize reflect usage: remove redundant TypeOf() call in aioCreate
- Pre-allocate kqueue changes slice on BSD