End the watch session on Discard, plus start-flow UX tweaks

Watch-side follow-through for the End Workout flow:
- The phone now pushes an authoritative set (in-progress, not-started, and
  completed within 24h) instead of the 25 most-recent workouts, and the watch
  prunes any workout absent from it. So a Discard/Delete (or a completed run aging
  out) drops off the watch, empties its active list, and ends the HKWorkoutSession
  — fixing the persistent wrist-raise re-foregrounding. The watch never originates
  a workout, so pruning can't lose local data; the 24h grace keeps a just-finished
  run on screen. The gate pops if the run you're viewing is pruned.

UX tweaks:
- The in-workout ⋯ is now a pull-down Menu (Add Exercise / End Workout) rather than
  an action sheet.
- Starting a split while another workout is still active now prompts to end the
  current one(s) — keeping their progress — or run in parallel. Wired into both
  start paths (the split picker and "Start This Split"), via a shared
  WorkoutDocument.endKeepingProgress() helper.

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

Workouts/Views/WorkoutLogs/WorkoutLogsView.swift

@@ -114,12 +114,23 @@ struct SplitPickerSheet: View {
     @Query(sort: [SortDescriptor(\Split.order), SortDescriptor(\Split.name)])
     private var splits: [Split]
 
+    @Query(sort: \Workout.start, order: .reverse)
+    private var workouts: [Workout]
+
+    /// Set when the user picks a split while other workouts are still going — drives the
+    /// "end the current one(s) or run in parallel?" prompt.
+    @State private var splitAwaitingConfirmation: Split?
+
+    private var activeWorkouts: [Workout] {
+        workouts.filter { $0.status == .inProgress || $0.status == .notStarted }
+    }
+
     var body: some View {
         NavigationStack {
             List {
                 ForEach(splits) { split in
                     Button {
-                        startWorkout(with: split)
+                        confirmAndStart(with: split)
                     } label: {
                         HStack {
                             Image(systemName: split.systemImage)
@@ -141,11 +152,58 @@ struct SplitPickerSheet: View {
                     }
                 }
             }
+            .confirmationDialog(
+                activePromptTitle,
+                isPresented: Binding(
+                    get: { splitAwaitingConfirmation != nil },
+                    set: { if !$0 { splitAwaitingConfirmation = nil } }
+                ),
+                titleVisibility: .visible,
+                presenting: splitAwaitingConfirmation
+            ) { split in
+                Button("End Current & Start New") { endActiveThenStart(with: split) }
+                Button("Start in Parallel") { start(with: split) }
+                Button("Cancel", role: .cancel) { splitAwaitingConfirmation = nil }
+            } message: { _ in
+                Text(activePromptMessage)
+            }
         }
     }
 
-    private func startWorkout(with split: Split) {
-        let start = Date()
+    private var activePromptTitle: String {
+        activeWorkouts.count == 1 ? "Workout in Progress" : "\(activeWorkouts.count) Workouts in Progress"
+    }
+
+    private var activePromptMessage: String {
+        let n = activeWorkouts.count
+        let those = n == 1 ? "it" : "them"
+        return "You already have \(n == 1 ? "a workout" : "\(n) workouts") going. End \(those) first, or run this one alongside."
+    }
+
+    /// Prompt before starting if other workouts are still going; otherwise start straight away.
+    private func confirmAndStart(with split: Split) {
+        if activeWorkouts.isEmpty {
+            start(with: split)
+        } else {
+            splitAwaitingConfirmation = split
+        }
+    }
+
+    /// End every in-flight workout (keeping its progress), then start the picked split.
+    private func endActiveThenStart(with split: Split) {
+        let toEnd = activeWorkouts.map { WorkoutDocument(from: $0) }
+        splitAwaitingConfirmation = nil
+        Task {
+            for var doc in toEnd {
+                doc.endKeepingProgress()
+                await sync.save(workout: doc)
+            }
+        }
+        start(with: split)
+    }
+
+    private func start(with split: Split) {
+        let startDate = Date()
         let logs = split.exercisesArray.enumerated().map { index, exercise in
             WorkoutLogDocument(
                 id: ULID.make(),
@@ -160,7 +218,7 @@ struct SplitPickerSheet: View {
                 completed: false,
                 status: WorkoutStatus.notStarted.rawValue,
                 notes: nil,
-                date: start
+                date: startDate
             )
         }
 
@@ -170,11 +228,11 @@ struct SplitPickerSheet: View {
             id: ULID.make(),
             splitID: split.id,
             splitName: split.name,
-            start: start,
+            start: startDate,
             end: nil,
             status: WorkoutStatus.notStarted.rawValue,
-            createdAt: start,
-            updatedAt: start,
+            createdAt: startDate,
+            updatedAt: startDate,
             logs: logs
         )