feat: Implement latency profiling and guardrails for performance monitoring

- Added synthetic latency profiler scenarios and CLI scripts for baseline generation and regression checks.
- Introduced latency baseline and threshold artifacts for CI enforcement.
- Enhanced CI workflow with latency guardrail checks.
- Updated documentation to include latency profiling commands and performance metrics.
- Added unit tests for latency guardrail evaluation.

.gitignore

@@ -36,6 +36,7 @@ data/*.duckdb
 data/*.duckdb.wal
 data/*.duckdb.tmp
 logs/
+ops/performance/latest_profile.json
 
 # Node assets if used for frontend tooling
 node_modules/