Enable clock tools for persistent reasoning turns (#40942)

## What changed

- Default the current-time reminder and interruptible `clock.sleep` tool on for
  turns using persistent reasoning effort.
- Preserve explicit `features.current_time_reminder` settings and managed
  requirements, and gate reminder recording on the resolved feature state.

## Testing

- Cover configured, persistent, ordinary-effort, explicitly disabled, and
  managed-disabled clock setups.
- Verify review turns do not expose clock tools or current-time reminders.

GitOrigin-RevId: 4ff8805807ceeef374abd962b1d9e7c37f1fbd83