feat: certify codegen chat drafts through loop

packages/casan-harness/config/prompt-modes.yaml

@@ -1,6 +1,6 @@
 {
   "version": 1,
-  "mvp_modes": ["READ_ONLY", "OPERATOR", "BLOCK", "NOT_SUPPORTED"],
+  "mvp_modes": ["READ_ONLY", "OPERATOR", "CODEGEN", "BLOCK", "NOT_SUPPORTED"],
   "read_only": {
     "risk": "low",
     "gates": ["H4_INPUT", "H4_OUTPUT", "H5_CHAT_AUDIT", "H6_TOKEN"],
@@ -16,6 +16,11 @@
     "gates": ["H4_INPUT", "ACTION_GATE", "H4_OUTPUT", "H5_CHAT_AUDIT", "H6_TOKEN"],
     "needs_approval": false
   },
+  "codegen": {
+    "risk": "high",
+    "gates": ["H4_INPUT", "H4_ARTIFACT_SCAN", "LOOP_GATE", "H5_CHAT_AUDIT"],
+    "needs_approval": true
+  },
   "block": {
     "risk": "high",
     "gates": ["H4_INPUT", "H5_CHAT_AUDIT"],
@@ -62,5 +67,12 @@
     "build evidence pack",
     "verify pack",
     "verify evidence pack"
+  ],
+  "codegen_terms": [
+    "generate code",
+    "draft code",
+    "write code",
+    "sourcegen",
+    "codegen"
   ]
 }