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

SCHEMA.md

@@ -154,7 +154,7 @@ veto seed resurrection forever).
 `0` none · `1` weight · `2` duration
 
 **WorkoutActivityType** (Int — on `SplitDocument.activityType`):
-`0` traditionalStrength · `1` functionalStrength · `2` hiit · `3` coreTraining · `4` cardio · `5` cycling
+`0` traditionalStrength · `1` functionalStrength · `2` hiit · `3` coreTraining · `4` cardio · `5` cycling · `6` warmUp · `7` stretching · `8` mindAndBody
 
 **MetricSource** (String — on `WorkoutMetrics.source`):
 `watch`, `phoneEstimate`