Mirror a live Apple Watch run on a propped-up iPhone

Add an ephemeral live-run presence channel (separate from the durable
iCloud progress sync) so a propped-up iPhone can mirror the Watch's
Ready → work/rest → Finish flow in real time as the user swipes.

Watch drives, phone mirrors (read-only), so there's no echo loop:
- Watch's ExerciseProgressView broadcasts a LiveProgress frame on every
  phase transition (and an ended signal on leave) via sendMessage,
  reachable-only — throwaway presence, never written to iCloud.
- Timers ride as wall-clock anchors (Date kept native in the WC dict to
  preserve sub-second precision), so both devices count independently
  off shared start times and stay in lockstep without streaming ticks.
- Phone holds a transient LiveRunState; ContentView auto-presents a
  read-only LiveProgressMirrorView full-screen cover while a run is live.

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

Workouts Watch App/Connectivity/WatchConnectivityBridge.swift

@@ -23,6 +23,10 @@ final class WatchConnectivityBridge: NSObject {
     private(set) var editingWorkoutID: String?
     private(set) var editingSplitID: String?
 
+    /// Monotonic sequence stamped on each live-run frame, so the phone mirror can drop a
+    /// stale / out-of-order delivery.
+    private var liveVersion = 0
+
     private var context: ModelContext { container.mainContext }
 
     init(container: ModelContainer) {
@@ -58,6 +62,26 @@ final class WatchConnectivityBridge: NSObject {
         sendToPhone(doc)
     }
 
+    // MARK: - Live run mirror (ephemeral; reachable-only)
+
+    /// Broadcast where the run flow currently is, so a propped-up iPhone can mirror it. Sent
+    /// over `sendMessage` only when the phone is reachable — this is throwaway presence, so
+    /// there's no guaranteed-delivery fallback (a queued frame would be stale on arrival).
+    func sendLiveProgress(_ frame: LiveProgress) {
+        guard let session, session.activationState == .activated, session.isReachable else { return }
+        liveVersion += 1
+        var stamped = frame
+        stamped.version = liveVersion
+        session.sendMessage(WCPayload.encodeLiveProgress(stamped), replyHandler: nil, errorHandler: { _ in })
+    }
+
+    /// Tell the phone to stop mirroring this run (the user left the progress flow).
+    func sendLiveEnded(workoutID: String, logID: String) {
+        guard let session, session.activationState == .activated, session.isReachable else { return }
+        session.sendMessage(WCPayload.encodeLiveEnded(workoutID: workoutID, logID: logID),
+                            replyHandler: nil, errorHandler: { _ in })
+    }
+
     // MARK: - Internal
 
     private func sendToPhone(_ doc: WorkoutDocument) {