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.

ops/performance/latency_thresholds.json

@@ -0,0 +1,16 @@
+{
+  "default": {
+    "p95_ms": 3.0,
+    "p99_ms": 3.5
+  },
+  "scenarios": {
+    "execution_spike": {
+      "p95_ms": 3.2,
+      "p99_ms": 3.8
+    },
+    "reconnect_storm": {
+      "p95_ms": 3.4,
+      "p99_ms": 4.0
+    }
+  }
+}