Performance benchmarking and tuning

**Depends on**: #29, #35

Performance validation:
- Run full benchmark suite
- Verify P99 < 5ms
- Verify throughput > 100k ops/sec
- Verify view change < 300ms
- Profile and optimize hot paths

**Acceptance**:
- [ ] All targets met
- [ ] No regressions
- [ ] Profile shows no bottlenecks