fix: Clear RPC channel for faster shutdown

packages/opencode/src/cli/cmd/tui/worker.ts

@@ -140,10 +140,14 @@ export const rpc = {
     await Promise.race([
       Instance.disposeAll(),
       new Promise((resolve) => {
-        setTimeout(resolve, 5000)
+        setTimeout(resolve, 5000).unref()
       }),
     ])
     if (server) server.stop(true)
+    // Clear the Rpc message channel so the worker's event loop can drain and
+    // exit naturally. Without this, the active onmessage handle keeps the
+    // worker alive even after all async work is done.
+    onmessage = null
   },
 }