## Why
Goal-first and forked threads could create rollouts without recording their
effective thread settings. Resuming those threads after a restart could then
use current configuration instead of the settings selected when the thread was
created.
## What changed
- Persist a `thread_settings_applied` item when a goal first materializes a
rollout, including a follow-up snapshot if settings changed concurrently.
- Append each fork's effective settings after its copied history so they take
precedence over inherited settings during resume.
- Centralize conversion from `ThreadConfigSnapshot` to
`ThreadSettingsSnapshot`.
## Testing
Added coverage that restarts the app server and verifies goal-first and forked
threads retain their respective `approvals_reviewer` settings.
GitOrigin-RevId: 6cb9aaae73bbe9ca432831cff7e826f95ffd6d01
Dylan Hurd
1836ae0612