Make the live run two-way: drive from either device

The propped-up iPhone now runs the real ExerciseProgressView for a live
watch workout instead of a read-only mirror, and the live-run channel is
symmetric — either device can drive the flow and the other follows.

Each page transition is classified human / auto / remote: only human
transitions (swipe, Start, One More, swipe-back reset) are broadcast and
recorded by the actor; auto-advances (rest / timed-work countdown) record
locally but aren't sent, since both devices reach them independently off
the shared wall-clock anchors; an applied remote frame jumps the page
without re-recording or re-broadcasting. That rule is also what stops an
echo loop.

- PhoneConnectivityBridge gains sendLiveProgress/sendLiveEnded (the
  missing phone->watch direction); WatchConnectivityBridge receives
  frames into an observable liveIncoming via a new didReceiveMessage
  route. Both share one increasing per-run version sequence so the
  stale-frame guard works across the two devices' counters.
- Both ExerciseProgressViews gain an incomingFrame input + applyIncoming
  (syncing setCount for a remote One More); the iPhone one gains the
  liveSnapshot/broadcast machinery the watch already had.
- New LiveRunCoverView wraps the real driver for the cover (resolves the
  workout, persists via SyncEngine, wires the live channel + close);
  ContentView presents it; LiveProgressMirrorView is removed.

Claude-Session: https://claude.ai/code/session_01SCv7zvGFcKy47KSTnTLxRe

CHANGELOG.md

@@ -1,6 +1,6 @@
 **June 2026**
 
-Prop your iPhone up during an Apple Watch workout and it now mirrors the live run — the same Ready → work/rest → Finish flow with running timers — following along set by set as you swipe on the watch.
+Prop your iPhone up during an Apple Watch workout and it now runs the same live flow side by side — Ready → work/rest → Finish with running timers — and you can drive from either device: swipe ahead, finish a set, or add one on whichever is closer, and the other follows along. Automatic moves, like a rest timer running out, advance both devices on their own.
 
 Editing an exercise or split on iPhone now steps the Apple Watch out of that workout, showing it as "Editing on iPhone" until you're done — so the watch never keeps running an exercise whose plan you're changing.