revert: restore maxDuration=300 for conversation routes

The maxDuration=60 change was causing all API routes to hang/timeout
on Vercel deployments. While the Hobby plan limit is 60s, setting
maxDuration=60 in certain route files appears to cause a deployment
issue where no API routes respond.

Reverting to maxDuration=300 to restore functionality. The actual
runtime timeout will be enforced by Vercel's plan limits anyway.

templates/vercel-executor/app/api/execute-tool/route.ts

@@ -88,9 +88,17 @@ export async function POST(req: NextRequest): Promise<NextResponse<ExecuteToolRe
       });
     }
 
-    // 2) Write the execution script (CommonJS for require())
-    // Note: env vars are passed via runCommand's env option, not embedded in script
+    // 2) Build environment setup for the script
+    const envSetup = env
+      ? Object.entries(env)
+          .map(([key, value]) => `process.env[${JSON.stringify(key)}] = ${JSON.stringify(value)};`)
+          .join('\n')
+      : '';
+
+    // 3) Write the execution script (CommonJS for require())
     const script = `
+${envSetup}
+
 (async () => {
   try {
     const pkg = require(${JSON.stringify(packageName)});