Add X-MCP-Toolsets header and fix Authorization header quoting in Copilot action MCP config

Author: austenstone

.github/actions/copilot/action.yml

@@ -111,7 +111,8 @@ runs:
               "type": "http",
               "url": "https://api.githubcopilot.com/mcp/readonly",
               "headers": {
-                "Authorization": "Bearer '"$GH_TOKEN"'"
+                "Authorization": "Bearer '$GH_TOKEN'",
+                "X-MCP-Toolsets": "all"
               },
               "tools": ["*"]
             }