chore(aiwg): adopt shared BT6 maintainer workflow (#148)

* docs(policy): allow low-impact contributor courtesy cleanup

* chore(aiwg): migrate to shared BT6 maintainer plugin

* chore: reconcile delivery validation

.aiwg/plugins/bt6-maintainer/payload/manifest.json

@@ -0,0 +1,34 @@
+{
+  "id": "bt6-maintainer",
+  "type": "addon",
+  "name": "bt6-maintainer",
+  "version": "0.2.0",
+  "description": "Cross-repository queue, review, issue, provider-trust, and merge stewardship for BT6 research and support tooling.",
+  "manifestVersion": "1",
+  "platforms": {
+    "claude": "full",
+    "codex": "full"
+  },
+  "keywords": [
+    "bt6",
+    "maintainer",
+    "research-tooling",
+    "support-tooling",
+    "repository-operations",
+    "pull-requests",
+    "issues",
+    "external-providers",
+    "trust-boundaries",
+    "merge-train",
+    "provenance"
+  ],
+  "deployment": {
+    "pathTemplate": ".{platform}/skills/{id}.md"
+  },
+  "addonConfig": {
+    "entry": {
+      "skills": "skills/",
+      "agents": "agents/"
+    }
+  }
+}