fix(external): align microsoft-docs version and pin source SHA

Set microsoft-docs version to 0.3.1 to match upstream plugin.json and
pin source to MicrosoftDocs/mcp HEAD f8ffde1 so installs are reproducible
and updates are detected correctly.

Fixes #4334

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: a1751e61-818d-4ddc-b7e9-2bd62f70f4ed

plugins/external.json

@@ -1055,7 +1055,7 @@
   {
     "name": "microsoft-docs",
     "description": "Access official Microsoft documentation, API references, and code samples for Azure, .NET, Windows, and more.",
-    "version": "1.0.0",
+    "version": "0.3.1",
     "author": {
       "name": "Microsoft",
       "url": "https://www.microsoft.com"
@@ -1077,7 +1077,8 @@
     "repository": "https://github.com/MicrosoftDocs/mcp",
     "source": {
       "source": "github",
-      "repo": "MicrosoftDocs/mcp"
+      "repo": "MicrosoftDocs/mcp",
+      "sha": "f8ffde185dfd232dbf5d187c22ce299eadc3d583"
     }
   },
   {