chore(orchestrator): Add Phase 4 summary to learnings

Phase 4: 12/12 tasks, 97% variance (estimates consistently low).
Closed issue #347.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/orchestrator-learnings.json

@@ -172,7 +172,29 @@
       "captured_at": "2026-02-05T19:05:00Z"
     }
   ],
-  "phase_summaries": [],
+  "phase_summaries": [
+    {
+      "phase": 4,
+      "name": "Remaining Medium Findings",
+      "issue": "#347",
+      "total_tasks": 12,
+      "completed": 12,
+      "failed": 0,
+      "deferred": 0,
+      "total_estimate_k": 117,
+      "total_actual_k": 231,
+      "variance_pct": 97,
+      "analysis": "Phase 4 estimates consistently under-predicted actual usage. Average task used 2x estimated tokens. Primary driver: DTO creation and comprehensive test suites expand scope beyond the core fix. The N+1 query fix (MS-P4-009) and TOCTOU race fix (MS-P4-010) were particularly complex. All 12 tasks completed successfully with zero failures.",
+      "test_counts": {
+        "api": 2397,
+        "web": 653,
+        "orchestrator": 642,
+        "shared": 17,
+        "ui": 11
+      },
+      "completed_at": "2026-02-06T14:22:00Z"
+    }
+  ],
   "proposed_adjustments": [
     {
       "category": "AUTH_ADD",