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/contracts/reviewer-code.schema.json

@@ -0,0 +1,46 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "title": "Code Reviewer Output",
+  "type": "object",
+  "required": ["task_id", "verdict", "checked_guard_ids", "checked_quality_gate_ids", "findings"],
+  "properties": {
+    "task_id": { "type": "string", "minLength": 1 },
+    "verdict": { "type": "string", "enum": ["pass", "fail"] },
+    "checked_guard_ids": {
+      "type": "array",
+      "minItems": 1,
+      "items": {
+        "type": "string",
+        "pattern": "^GR-(CORE|TEST|UI)-[A-Z0-9]{3,}$"
+      }
+    },
+    "checked_quality_gate_ids": {
+      "type": "array",
+      "minItems": 1,
+      "items": {
+        "type": "string",
+        "pattern": "^QG-[0-9]{3}$"
+      }
+    },
+    "findings": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "required": ["id", "severity", "rule_ref", "summary", "file"],
+        "properties": {
+          "id": { "type": "string", "minLength": 1 },
+          "severity": { "type": "string", "enum": ["low", "medium", "high", "critical"] },
+          "rule_ref": {
+            "type": "string",
+            "pattern": "^(GR-(CORE|TEST|UI)-[A-Z0-9]{3,}|QG-[0-9]{3})$"
+          },
+          "summary": { "type": "string", "minLength": 1 },
+          "file": { "type": "string", "minLength": 1 },
+          "fix_required": { "type": "string" }
+        },
+        "additionalProperties": false
+      }
+    }
+  },
+  "additionalProperties": false
+}