Park the Watch run while iPhone edits an exercise or split

Publish an exclusive-edit lock (editingWorkoutID / editingSplitID) in the
phone→watch application context. While the phone has a workout's exercise
(ExerciseView) or a split (SplitDetailView) open in an editor, the watch pops
out of that run, blocks re-entry, and shows it as "Editing on iPhone" — so the
two devices never drive the same run at once and the watch can't clobber the
phone's edit with a stale optimistic write. The lock clears when the editor
closes; absent keys in the latest-wins context mean "not editing".

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

Shared/Connectivity/WCPayload.swift

@@ -11,18 +11,26 @@ enum WCPayload {
     static let workoutKey = "workout"
     static let restSecondsKey = "restSeconds"
     static let doneCountdownSecondsKey = "doneCountdownSeconds"
+    static let editingWorkoutIDKey = "editingWorkoutID"
+    static let editingSplitIDKey = "editingSplitID"
 
     static let workoutUpdateType = "workoutUpdate"   // watch → phone (one workout)
     static let requestSyncType = "requestSync"       // watch → phone (please push state)
 
     // MARK: - Phone → Watch (application context: latest-state-wins)
 
-    static func encodeState(splits: [SplitDocument], workouts: [WorkoutDocument], restSeconds: Int, doneCountdownSeconds: Int) -> [String: Any] {
+    /// `editingWorkoutID` / `editingSplitID` are an exclusive-edit lock: while the phone
+    /// has a workout's exercise (or a split) open in an editor, the watch parks any
+    /// matching run and locks re-entry, so only one device owns the run at a time. They're
+    /// part of the same latest-wins context — absent keys mean "not editing" (lock clear).
+    static func encodeState(splits: [SplitDocument], workouts: [WorkoutDocument], restSeconds: Int, doneCountdownSeconds: Int, editingWorkoutID: String?, editingSplitID: String?) -> [String: Any] {
         var dict: [String: Any] = [:]
         if let s = try? DocumentCoder.encoder.encode(splits) { dict[splitsKey] = s }
         if let w = try? DocumentCoder.encoder.encode(workouts) { dict[workoutsKey] = w }
         dict[restSecondsKey] = restSeconds
         dict[doneCountdownSecondsKey] = doneCountdownSeconds
+        if let editingWorkoutID { dict[editingWorkoutIDKey] = editingWorkoutID }
+        if let editingSplitID { dict[editingSplitIDKey] = editingSplitID }
         return dict
     }
 
@@ -40,6 +48,10 @@ enum WCPayload {
 
     static func decodeDoneCountdownSeconds(_ dict: [String: Any]) -> Int? { dict[doneCountdownSecondsKey] as? Int }
 
+    static func decodeEditingWorkoutID(_ dict: [String: Any]) -> String? { dict[editingWorkoutIDKey] as? String }
+
+    static func decodeEditingSplitID(_ dict: [String: Any]) -> String? { dict[editingSplitIDKey] as? String }
+
     // MARK: - Watch → Phone (a single updated workout)
 
     static func encodeWorkoutUpdate(_ workout: WorkoutDocument) -> [String: Any] {