Restructure into a three-tab app with Progress, goals, and Meditation

The UX redesign's first landing (spec in UX-REDESIGN.md): ContentView
becomes a Today / Progress / Settings TabView, "Routine" replaces
"Split" in every user-facing string and view name (code-level types
keep their names), and workout starting moves to shared
WorkoutStarter / StartedWorkoutNavigator plumbing.

- New Progress tab: weekly goal streaks, workout trends, per-exercise
  weight progression, achievements, and the full history list
  (WorkoutLogsView -> WorkoutHistoryView).
- Goals: stable categories workouts roll up to, managed from Settings.
- New Meditation exercise + starter routine; timed sits record to
  Apple Health as Mind & Body sessions.

Claude-Session: https://claude.ai/code/session_012qw2itfzKyEJ1HpsFt8Ex4

Workouts/Views/Exercises/ExerciseAddEditView.swift

@@ -18,8 +18,8 @@ struct ExerciseAddEditView: View {
 
     // The exercise entity provides initial values (read-only).
     let exercise: Exercise
-    // The parent split is needed to rebuild and save the SplitDocument.
-    let split: Split
+    // The parent routine is needed to rebuild and save the RoutineDocument.
+    let routine: Routine
 
     // Local editable state
     @State private var exerciseName: String
@@ -37,9 +37,9 @@ struct ExerciseAddEditView: View {
     @State private var machineSettings: [MachineSetting]
     @AppStorage("weightUnit") private var weightUnit: WeightUnit = .lb
 
-    init(exercise: Exercise, split: Split) {
+    init(exercise: Exercise, routine: Routine) {
         self.exercise = exercise
-        self.split = split
+        self.routine = routine
 
         // The tens/ones pickers step whole values; a fractional stored weight
         // shows (and saves back) its whole part until UX #3's UI lands.
@@ -197,7 +197,7 @@ struct ExerciseAddEditView: View {
         let newWeight = weightTens + weightOnes
         let durationSecs = minutes * 60 + seconds
 
-        var doc = SplitDocument(from: split)
+        var doc = RoutineDocument(from: routine)
         if let idx = doc.exercises.firstIndex(where: { $0.id == exercise.id }) {
             doc.exercises[idx].name = exerciseName
             doc.exercises[idx].sets = sets
@@ -209,6 +209,6 @@ struct ExerciseAddEditView: View {
             doc.exercises[idx].machineSettings = machineEnabled ? machineSettings : nil
         }
         doc.updatedAt = Date()
-        Task { await sync.save(split: doc) }
+        Task { await sync.save(routine: doc) }
     }
 }