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": "c003e96852fa9534aee40b2cb85a96d8bd38732d",
-      "syncedAt": "2026-10-09T10:26:29Z"
+      "commit": "2d3f1cd436b18ea12f24130de4df781355925b08",
+      "syncedAt": "2026-10-09T16:00:00Z"
     },
     {
       "id": "frontend-slides",
@@ -177,8 +177,8 @@
       "repo": "https://github.com/mattpocock/skills.git",
       "ref": "main",
       "adapter": "skill-collection",
-      "commit": "b0618bc436ad893b3c5e84e55fba86586d34a404",
-      "syncedAt": "2026-10-08T15:59:59Z"
+      "commit": "49dd158d1076134a641b33efb035946536778336",
+      "syncedAt": "2026-10-09T16:00:00Z"
     },
     {
       "id": "updating-gitea-repositories",
@@ -258,8 +258,8 @@
       "repo": "https://github.com/vercel/next.js.git",
       "ref": "canary",
       "adapter": "skill-collection",
-      "commit": "76bed42c1b10c623dcfc63d2f6a80940bf79e157",
-      "syncedAt": "2026-10-09T10:26:29Z"
+      "commit": "2d0da21235fdf3554244bf4c5c19369fbcd6b37b",
+      "syncedAt": "2026-10-09T16:00:00Z"
     },
     {
       "id": "shuorenhua",