Sync third-party and MCP marketplace plugins

Constraint: Public skills are published only by explicit administrator action unless they are tracked third-party market sources.
Confidence: high
Scope-risk: narrow
Directive: Keep private/internal skills out of the public marketplace and preserve normal incremental market Git history.
Tested: Marketplace validation passed.

plugins/codex/.agents/plugins/marketplace.json

@@ -184,6 +184,42 @@
       },
       "category": "Developer Tools"
     },
+    {
+      "name": "embedded-app-pc-debug",
+      "source": {
+        "source": "local",
+        "path": "./plugins/embedded-app-pc-debug"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Developer Tools"
+    },
+    {
+      "name": "firmware-app-development",
+      "source": {
+        "source": "local",
+        "path": "./plugins/firmware-app-development"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Developer Tools"
+    },
+    {
+      "name": "firmware-lowlevel-development",
+      "source": {
+        "source": "local",
+        "path": "./plugins/firmware-lowlevel-development"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Developer Tools"
+    },
     {
       "name": "generate-agents-md",
       "source": {