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

@@ -132,8 +132,8 @@
       "repo": "https://github.com/shadcn-ui/ui.git",
       "ref": "main",
       "adapter": "claude-skill",
-      "commit": "4233ed1caded8c38f4bc14b14afe1f93ebcaf966",
-      "syncedAt": "2026-10-14T16:00:00Z"
+      "commit": "c2477f311c19982ef6e246085438e6cfec3e35ea",
+      "syncedAt": "2026-10-15T16:00:00Z"
     },
     {
       "id": "frontend-slides",
@@ -258,8 +258,8 @@
       "repo": "https://github.com/vercel/next.js.git",
       "ref": "canary",
       "adapter": "skill-collection",
-      "commit": "0b3693ddd5fca101fe6d286849a980ddc1bf0650",
-      "syncedAt": "2026-10-15T03:03:03Z"
+      "commit": "fb20d9af8b89e2507466702d6844f9e984012fb8",
+      "syncedAt": "2026-10-15T16:00:00Z"
     },
     {
       "id": "shuorenhua",