Add sdk.paths and sdk.errorMessage to global.json (#11074)

* Initial plan

* Add sdk.paths and sdk.errorMessage to global.json

Co-authored-by: davidfowl <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: davidfowl <[email protected]>

Author: Copilot

global.json

@@ -2,7 +2,9 @@
   "sdk": {
     "version": "10.0.100-preview.5.25277.114",
     "rollForward": "major",
-    "allowPrerelease": true
+    "allowPrerelease": true,
+    "paths": [ ".dotnet", "$host$" ],
+    "errorMessage": "The .NET SDK could not be found. Run ./restore.sh (Linux/macOS) or ./restore.cmd (Windows) to install the local SDK."
   },
   "tools": {
     "dotnet": "10.0.100-preview.5.25277.114",