fix: wait for stdout to flush in generate command (#3821)

packages/opencode/src/cli/cmd/generate.ts

@@ -5,6 +5,14 @@ export const GenerateCommand = {
   command: "generate",
   handler: async () => {
     const specs = await Server.openapi()
-    process.stdout.write(JSON.stringify(specs, null, 2))
+    const json = JSON.stringify(specs, null, 2)
+    
+    // Wait for stdout to finish writing before process.exit() is called
+    await new Promise<void>((resolve, reject) => {
+      process.stdout.write(json, (err) => {
+        if (err) reject(err)
+        else resolve()
+      })
+    })
   },
 } satisfies CommandModule