feat(casan): add native plugin facade

.codex-plugin/plugin.json

@@ -0,0 +1,30 @@
+{
+  "name": "casan",
+  "version": "1.0.7",
+  "description": "Native Codex operator facade for the CASAN governed AI coding assurance runtime.",
+  "author": {
+    "name": "CASAN Team"
+  },
+  "license": "Proprietary",
+  "keywords": [
+    "agentic-coding",
+    "assurance",
+    "governance",
+    "security",
+    "audit"
+  ],
+  "skills": "./skills/",
+  "interface": {
+    "displayName": "CASAN",
+    "shortDescription": "Governed AI coding assurance",
+    "longDescription": "Adopt, diagnose, verify, and operate the CASAN assurance runtime from Codex while preserving project-local hook trust and the versioned shared runtime.",
+    "developerName": "CASAN Team",
+    "category": "Developer Tools",
+    "capabilities": [
+      "Project adoption",
+      "Assurance verification",
+      "Governed execution"
+    ],
+    "defaultPrompt": "Use $casan to adopt and verify CASAN in this project."
+  }
+}