Save workouts to Apple Health with live watch metrics and a post-workout summary

Watch sessions now run an HKLiveWorkoutBuilder: heart rate and active
energy are collected live (shown in an in-workout HUD), saved to Health
as a real HKWorkout on completion, and carried back to the phone as
WorkoutMetrics on the workout document. Phone-only workouts get an
estimated Health workout (MET x bodyweight x duration) after a 10s
debounce that a late-arriving watch session cancels; a launch sweep
backfills workouts completed within the last day. Dedupe is keyed on
metrics.healthKitWorkoutUUID plus the metrics source.

Splits gain an activity type (strength, functional, HIIT, core, cardio,
cycling) that categorizes the Health workout and picks the MET value.
A post-workout summary sheet (duration, calories, avg/max HR, HR zones,
total volume) fills in live and is also shown on completed workouts.
Weights can now display in lb or kg (display-only relabel), synced to
the watch over the existing application context.

WorkoutDocument schema 1->2 (metrics are irreplaceable, so older apps
must quarantine rather than strip them); cache schema 2 rebuilds the
SwiftData store with the new metric columns. Deleting a workout in the
app intentionally leaves its Health record in place.

Workouts/Views/Splits/SplitAddEditView.swift

@@ -21,6 +21,7 @@ struct SplitAddEditView: View {
     @State private var name: String = ""
     @State private var color: String = "indigo"
     @State private var systemImage: String = "dumbbell.fill"
+    @State private var activityType: WorkoutActivityType = .traditionalStrength
     @State private var showingIconPicker: Bool = false
     @State private var showingDeleteConfirmation: Bool = false
 
@@ -33,6 +34,7 @@ struct SplitAddEditView: View {
             _name = State(initialValue: split.name)
             _color = State(initialValue: split.color)
             _systemImage = State(initialValue: split.systemImage)
+            _activityType = State(initialValue: split.activityTypeEnum)
         }
     }
 
@@ -71,6 +73,18 @@ struct SplitAddEditView: View {
                     }
                 }
 
+                Section {
+                    Picker("Activity Type", selection: $activityType) {
+                        ForEach(WorkoutActivityType.allCases, id: \.self) { type in
+                            Label(type.displayName, systemImage: type.systemImage).tag(type)
+                        }
+                    }
+                } header: {
+                    Text("Activity Type")
+                } footer: {
+                    Text("Determines how this workout is categorized in Apple Health and how it credits your Activity rings.")
+                }
+
                 if let split = split {
                     Section(header: Text("Exercises")) {
                         NavigationLink {
@@ -136,6 +150,7 @@ struct SplitAddEditView: View {
             doc.name = name
             doc.color = color
             doc.systemImage = systemImage
+            doc.activityType = activityType.rawValue
             doc.updatedAt = Date()
             Task { await sync.save(split: doc) }
         } else {
@@ -150,7 +165,8 @@ struct SplitAddEditView: View {
                 order: existing.count,
                 createdAt: Date(),
                 updatedAt: Date(),
-                exercises: []
+                exercises: [],
+                activityType: activityType.rawValue
             )
             Task { await sync.save(split: doc) }
         }

Workouts/Views/Splits/SplitDetailView.swift

@@ -21,6 +21,7 @@ struct SplitDetailView: View {
     @State private var showingSplitEditSheet: Bool = false
     @State private var itemToEdit: Exercise? = nil
     @State private var itemToDelete: Exercise? = nil
+    @AppStorage("weightUnit") private var weightUnit: WeightUnit = .lb
 
     var body: some View {
         Form {
@@ -36,7 +37,7 @@ struct SplitDetailView: View {
                     ForEach(sortedExercises) { item in
                         ListItem(
                             title: item.name,
-                            subtitle: "\(item.sets) × \(item.reps) × \(item.weight) lbs"
+                            subtitle: "\(item.sets) × \(item.reps) × \(weightUnit.format(item.weight))"
                         )
                         .swipeActions {
                             Button {