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 Watch AppTests/SessionEndPlannerTests.swift

@@ -19,7 +19,7 @@ struct SessionEndPlannerTests {
     private func workout(_ id: String, _ status: WorkoutStatus, start: Date = ts) -> WorkoutDocument {
         WorkoutDocument(
             schemaVersion: WorkoutDocument.currentSchemaVersion,
-            id: id, splitID: nil, splitName: nil, start: start, end: nil,
+            id: id, routineID: nil, routineName: nil, start: start, end: nil,
             status: status.rawValue, createdAt: start, updatedAt: start,
             logs: [], metrics: nil)
     }