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.

config/external-sources.lock.json

@@ -168,8 +168,8 @@
       "repo": "https://github.com/hugohe3/ppt-master.git",
       "ref": "main",
       "adapter": "claude-skill",
-      "commit": "cc8b722a24e9fb540e67c2d58a9ea3da534cd682",
-      "syncedAt": "2026-10-21T06:48:34Z"
+      "commit": "604ecdec8dd6a0405e1abdb49565430902373276",
+      "syncedAt": "2026-10-21T16:00:00Z"
     },
     {
       "id": "grill-me",
@@ -258,8 +258,8 @@
       "repo": "https://github.com/vercel/next.js.git",
       "ref": "canary",
       "adapter": "skill-collection",
-      "commit": "72895219d44df111ee6ac81e4eac10d81a5e5cbf",
-      "syncedAt": "2026-10-21T06:48:34Z"
+      "commit": "1984f672c01923e26a23ab24063d42a5263b1561",
+      "syncedAt": "2026-10-21T16:00:00Z"
     },
     {
       "id": "shuorenhua",