Tilt live_update adds initial_sync for pre-built images
For a pre-built image, add `initial_sync()` first in `live_update` to upload files from its `sync` paths when Tilt first observes a running container and after restarts. Then define `sync` steps and optional `run` triggers; during initial sync, untriggered `run` steps execute and triggered ones execute only when synced files match.
live_update=[
initial_sync(),
sync('./src', '/app/src'),
run('npm install', trigger=['./src/package.json']),
]