FitKit Pro

- Save to Health: optional HealthKit integration on the Watch app and in Fit-Kit timing tools, with per-tool activity types/metadata and per-exercise credit in playlists instead of all-or-nothing. - Circuit progress rings in the playlist runner's step row, supporting up to 4 nested rings per circuit with animated fill and outward growth from a fixed inner ring. - Always-On Display support for timing tool views (`isLuminanceReduced`). - Watch total-time previews and a circuit round indicator in the Playlist detail view, which now reacts live to iPhone-pushed updates. - `WatchCelebrationView`, a watch-sized completion celebration, wired into playlist and standalone tool completion. - Halfway/10-seconds audio cues and a done+wellDone completion sequence on watch Tempo; recovery-period countdown added to watch Metronome; Tempo countdown sounds and metronome up/down sounds.