AppHosting emulator: "TIMEOUT: Port 5002 on localhost was not active within 60000ms"

### [REQUIRED] Environment info

**firebase-tools:** 15.1.0

**Platform:** macOS

### [REQUIRED] Test case

### [REQUIRED] Steps to reproduce

Run firebase emulators:start, with apphosting enabled.
My Angular 20 app is served on localhost:4200
Wait 1 minute.

### [REQUIRED] Expected behavior

No error on the console. User should be able to continue developing.

### [REQUIRED] Actual behavior

After 1 minute of not browsing the app, this error appears on the console:
"TIMEOUT: Port 5002 on localhost was not active within 60000ms"
The app stops working on localhost:4200.

Start by reproducing with firebase emulators:start and App Hosting enabled while an Angular 20 app runs on localhost:4200 on macOS; observe the console for the 60-second Port 5002 timeout. Done means the emulator remains usable without that timeout and the app continues working after a minute without browsing.

Written by the indexing model from the issue text.