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/WorkoutLogs/PlanEditView.swift

@@ -163,13 +163,13 @@ struct PlanEditView: View {
         let exerciseName = doc.logs[i].exerciseName
         let workoutDoc = doc
 
-        // 2) Mirror the plan onto the matching exercise in the split template,
+        // 2) Mirror the plan onto the matching exercise in the routine template,
         // following the seed clone-on-edit redirect so a prior fork doesn't
         // silently break the mirror.
-        var splitDoc: SplitDocument?
-        if let splitID = doc.splitID,
-           let split = CacheMapper.fetchSplit(id: sync.currentSplitID(for: splitID), in: modelContext) {
-            var sDoc = SplitDocument(from: split)
+        var routineDoc: RoutineDocument?
+        if let routineID = doc.routineID,
+           let routine = CacheMapper.fetchRoutine(id: sync.currentRoutineID(for: routineID), in: modelContext) {
+            var sDoc = RoutineDocument(from: routine)
             if let ei = sDoc.exercises.firstIndex(where: { $0.name == exerciseName }) {
                 sDoc.exercises[ei].sets = sets
                 sDoc.exercises[ei].reps = reps
@@ -177,14 +177,14 @@ struct PlanEditView: View {
                 sDoc.exercises[ei].durationSeconds = totalSeconds
                 sDoc.exercises[ei].loadType = selectedLoadType.rawValue
                 sDoc.updatedAt = Date()
-                splitDoc = sDoc
+                routineDoc = sDoc
             }
         }
 
         Task {
             await sync.save(workout: workoutDoc)
-            if let splitDoc {
-                await sync.save(split: splitDoc)
+            if let routineDoc {
+                await sync.save(routine: routineDoc)
             }
         }
     }