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

WorkoutsTests/WorkoutDocumentMapperTests.swift

@@ -26,7 +26,7 @@ struct WorkoutDocumentMapperTests {
 
     @MainActor
     private func makeContext() throws -> ModelContext {
-        let schema = Schema([Split.self, Exercise.self, Workout.self, WorkoutLog.self])
+        let schema = Schema([Routine.self, Exercise.self, Workout.self, WorkoutLog.self])
         // cloudKitDatabase: .none matches WorkoutsModelContainer (see SeedLibraryTests).
         let config = ModelConfiguration(schema: schema, isStoredInMemoryOnly: true, cloudKitDatabase: .none)
         return ModelContext(try ModelContainer(for: schema, configurations: [config]))
@@ -63,7 +63,7 @@ struct WorkoutDocumentMapperTests {
         let context = try makeContext()
         let original = WorkoutDocument(
             schemaVersion: WorkoutDocument.currentSchemaVersion,
-            id: "01WORKOUTROUNDTRIP00000001", splitID: "SPLIT-42", splitName: "Push Day",
+            id: "01WORKOUTROUNDTRIP00000001", routineID: "RT-42", routineName: "Push Day",
             start: Self.start, end: Self.end, status: WorkoutStatus.completed.rawValue,
             createdAt: Self.created, updatedAt: Self.updated,
             logs: [
@@ -97,8 +97,8 @@ struct WorkoutDocumentMapperTests {
 
         // Spot-pin the load-bearing fields the whole-document `==` rolls up, so a future
         // regression names itself.
-        #expect(rebuilt.splitID == "SPLIT-42")
-        #expect(rebuilt.splitName == "Push Day")
+        #expect(rebuilt.routineID == "RT-42")
+        #expect(rebuilt.routineName == "Push Day")
         #expect(rebuilt.start == Self.start)
         #expect(rebuilt.end == Self.end)
         #expect(rebuilt.createdAt == Self.created)
@@ -131,7 +131,7 @@ struct WorkoutDocumentMapperTests {
         let context = try makeContext()
         let original = WorkoutDocument(
             schemaVersion: WorkoutDocument.currentSchemaVersion,
-            id: "01WORKOUTNOMETRICS0000001", splitID: nil, splitName: nil,
+            id: "01WORKOUTNOMETRICS0000001", routineID: nil, routineName: nil,
             start: Self.start, end: nil, status: WorkoutStatus.inProgress.rawValue,
             createdAt: Self.created, updatedAt: Self.updated,
             logs: [log(id: "LOG-X", name: "Plank", order: 0, status: .inProgress, startedAt: Self.startedAt)],
@@ -144,7 +144,7 @@ struct WorkoutDocumentMapperTests {
 
         #expect(rebuilt == original)
         #expect(rebuilt.metrics == nil)
-        #expect(rebuilt.splitID == nil)
+        #expect(rebuilt.routineID == nil)
         #expect(rebuilt.end == nil)
     }
 
@@ -156,7 +156,7 @@ struct WorkoutDocumentMapperTests {
         let context = try makeContext()
         let scrambled = WorkoutDocument(
             schemaVersion: WorkoutDocument.currentSchemaVersion,
-            id: "01WORKOUTLOGORDER00000001", splitID: "S", splitName: "S",
+            id: "01WORKOUTLOGORDER00000001", routineID: "S", routineName: "S",
             start: Self.start, end: Self.end, status: WorkoutStatus.completed.rawValue,
             createdAt: Self.created, updatedAt: Self.updated,
             logs: [
@@ -184,7 +184,7 @@ struct WorkoutDocumentMapperTests {
         let context = try makeContext()
         let first = WorkoutDocument(
             schemaVersion: WorkoutDocument.currentSchemaVersion,
-            id: "01WORKOUTREUPSERT00000001", splitID: "S", splitName: "S",
+            id: "01WORKOUTREUPSERT00000001", routineID: "S", routineName: "S",
             start: Self.start, end: nil, status: WorkoutStatus.inProgress.rawValue,
             createdAt: Self.created, updatedAt: Self.updated,
             logs: [