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

@@ -105,8 +105,8 @@
       "repo": "https://github.com/hugohe3/ppt-master.git",
       "ref": "main",
       "adapter": "claude-skill",
-      "commit": "b44cdfac5d88b912b92bdc87b2f87cd9afd91a48",
-      "syncedAt": "2026-09-15T07:53:22Z"
+      "commit": "be8089296767d3e8cf012e07ea31c8716591bad8",
+      "syncedAt": "2026-09-15T16:00:00Z"
     },
     {
       "id": "grill-me",
@@ -114,8 +114,8 @@
       "repo": "https://github.com/mattpocock/skills.git",
       "ref": "main",
       "adapter": "skill-collection",
-      "commit": "3cca18b368ae95cdbdebbff572ccafa662551015",
-      "syncedAt": "2026-09-04T16:00:00Z"
+      "commit": "959a8e9f1edc3adbe2f7e3054bb6fbefa6696260",
+      "syncedAt": "2026-09-15T16:00:00Z"
     },
     {
       "id": "updating-gitea-repositories",
@@ -177,8 +177,8 @@
       "repo": "https://github.com/vercel/next.js.git",
       "ref": "canary",
       "adapter": "skill-collection",
-      "commit": "e29a96a9eea4821af9fecd2edbd73e45e513e80d",
-      "syncedAt": "2026-09-15T09:16:34Z"
+      "commit": "bfcf687f5ab6f1e0577573eb209476cef802f5d7",
+      "syncedAt": "2026-09-15T16:00:00Z"
     },
     {
       "id": "shuorenhua",