## Why
Clients need a per-thread Daybreak toggle that survives restarts and can be
restored on resume without changing the access program of an active or future
turn.
## What changed
- Add experimental `daybreakEnabled` support to `thread/metadata/update` and
expose the saved value on thread responses.
- Store the preference in SQLite, including for threads without a first turn,
and preserve it through reads, resumes, reconciliation, and restarts.
- Copy the preference when forking a thread while keeping subsequent updates
independent.
- Keep `daybreakEnabled` separate from the per-turn `cyberAccessProgram` field;
app-server does not derive one from the other.
## Testing
- Cover persistence across restarts, cold reads, reconciliation, and forks.
- Verify metadata updates do not alter the access program of active or later
turns.
GitOrigin-RevId: bcf987a9fcd7b0ac8a88b1c8f0df06b33ed8ad6e
3921a30d6b