refactor: relocate agent-system/ to .agents/ with 7-role workflow restructure

Moves the agent workflow system from agent-system/ to .agents/ (dotfile convention).
Restructured from 5-role to 7-role pipeline: adds Analyst and splits Reviewer into
Code Reviewer + Security Reviewer. Removes all old workflow run artifacts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.agents/templates/execution-report.template.json

@@ -0,0 +1,39 @@
+{
+  "task_id": "TASK-0001",
+  "plan_ref": ".agents/runs/TASK-0001/plan.json",
+  "status": "done",
+  "changed_files": [
+    {
+      "path": "path/to/file",
+      "summary": "What changed"
+    }
+  ],
+  "guard_evidence": [
+    {
+      "guard_id": "GR-CORE-003",
+      "status": "pass",
+      "evidence": "Short evidence with file or test reference."
+    }
+  ],
+  "commands": [
+    {
+      "cmd": "docker compose exec php vendor/bin/phpunit",
+      "result": "pass"
+    }
+  ],
+  "quality_gate_results": [
+    {
+      "gate_id": "QG-001",
+      "result": "pass",
+      "notes": ""
+    }
+  ],
+  "test_results": [
+    {
+      "name": "test name",
+      "result": "pass",
+      "notes": ""
+    }
+  ],
+  "open_items": []
+}