fix mcp stdio server output (#391)

Author: brendanjryan

.changeset/fair-masks-hammer.md

@@ -0,0 +1,5 @@
+---
+'mppx': patch
+---
+
+Fixed MCP stdio startup and returned structured CLI command results without writing raw tool output to stdout.

src/bin.ts

@@ -1,4 +1,4 @@
 #!/usr/bin/env node
 import cli from './cli/cli.js'
 
-cli.serve().then(() => process.exit(0))
+await cli.serve()