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/HealthKit/WorkoutLauncher.swift

@@ -18,23 +18,26 @@ import HealthKit
 final class WorkoutLauncher {
     private let healthStore = HKHealthStore()
 
-    /// Strength/HIIT configuration handed to watchOS; the watch starts a session with
-    /// the same shape (see `WorkoutSessionManager`).
-    static func makeConfiguration() -> HKWorkoutConfiguration {
+    /// Configuration handed to watchOS; the watch starts a session with the same
+    /// shape (see `WorkoutSessionManager`). The activity type comes from the split so
+    /// the saved Health workout is categorized correctly.
+    static func makeConfiguration(activityType: HKWorkoutActivityType) -> HKWorkoutConfiguration {
         let configuration = HKWorkoutConfiguration()
-        configuration.activityType = .traditionalStrengthTraining
+        configuration.activityType = activityType
         configuration.locationType = .indoor
         return configuration
     }
 
     /// Ask watchOS to launch the Watch app into the workout. Best-effort: no-ops where
     /// HealthKit is unavailable (e.g. iPad without it) and silently tolerates a missing
-    /// or unreachable paired watch.
-    func launchWatchWorkout() {
+    /// or unreachable paired watch. Authorization is requested up front by
+    /// `WorkoutHealthWriter` at launch, so we only need the workout-share scope that
+    /// `startWatchApp(toHandle:)` itself requires.
+    func launchWatchWorkout(activityType: HKWorkoutActivityType) {
         guard HKHealthStore.isHealthDataAvailable() else { return }
         Task {
             try? await healthStore.requestAuthorization(toShare: [.workoutType()], read: [])
-            try? await healthStore.startWatchApp(toHandle: Self.makeConfiguration())
+            try? await healthStore.startWatchApp(toHandle: Self.makeConfiguration(activityType: activityType))
         }
     }
 }