chore: add clean step to build script to remove stale dist files

Author: Dev Agent Amelia

package.json

@@ -38,7 +38,8 @@
     "publish:npm": "node scripts/publish.mjs --npm",
     "publish:mcp": "node scripts/publish.mjs --mcp",
     "publish:dry": "node scripts/publish.mjs --dry",
-    "build": "tsc",
+    "clean": "node -e \"const {rmSync}=require('fs'); try{rmSync('dist',{recursive:true})}catch{}\"",
+    "build": "npm run clean && tsc",
     "dev": "tsx watch src/server.ts",
     "start": "node dist/server.js",
     "auth:setup": "node dist/setup-auth.js",