We're migrating our website to Railway and are trying to configure Healthcheck on our staging web service.
Setup:
- Rails 8.1 app running on Puma with 2 replicas
- Health endpoint: /up (Rails built-in)
- App listens on port 3000

Issue: On staging, every deploy fails with "1/1 replicas never became healthy". The healthcheck hits /up but gets "service unavailable" on all 11 attempts before the 5 minute retry window expires.
The app has a startup process that clones external git repos and downloads assets before Puma is ready to serve requests. This startup process takes longer than the 5 minute healthcheck window allows.

Logs: ====================
Starting Healthcheck
====================
Path: /up
Retry window: 5m0s
Attempt #1 failed with service unavailable. Continuing to retry for 4m49s ... Attempt #11 failed with service unavailable. Continuing to retry for 8s
1/1 replicas never became healthy! Healthcheck failed!

How can we configure this Healthcheck correctly?