fix: wrap github MCP config with mcpServers in issue-triage workflow

Update the MCP configuration structure to properly wrap the github
server configuration within an mcpServers object, matching the
expected format for MCP config files.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/issue-triage.yml

@@ -23,6 +23,7 @@ jobs:
           mkdir -p /tmp/mcp-config
           cat > /tmp/mcp-config/mcp-servers.json << 'EOF'
           {
+            "mcpServers": {
               "github": {
                 "command": "docker",
                 "args": [
@@ -38,6 +39,7 @@ jobs:
                 }
               }
             }
+          }
           EOF
 
       - name: Create triage prompt