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

Exercise Library/COVERAGE.md

@@ -40,6 +40,7 @@ it is a considered exclusion, not a gap.
 | Core flexion | Abdominal | — | Crunch, Reverse Crunch, Leg Raises |
 | Mobility / warm-up | — | — | Cat-Cow, March in Place, Leg Swings, Neck Rolls, Arm Circles, Torso Twist, Standing Side Bend, Hip Circles |
 | Static stretch | — | — | Standing Forward Fold, Standing Quad Stretch, Standing Calf Stretch, Chest Opener, Overhead Triceps Stretch, Kneeling Hip Flexor Stretch, Butterfly Stretch, Cobra Stretch, Child's Pose |
+| Mindfulness / breath | — | — | Meditation |
 
 ## Gym-floor census
 
@@ -60,6 +61,7 @@ entries) a user logging by that station's name will find.
 | Floor / mat | Bodyweight Squat, Push-Up, Crunch, Glute Bridge, Plank, Side Plank, Bird Dog, Dead Bug, Hollow Body Hold, Leg Raises, Reverse Crunch, Cat-Cow |
 | Open floor (warm-up / mobility) | March in Place, Leg Swings, Neck Rolls, Arm Circles, Torso Twist, Standing Side Bend, Hip Circles, Standing Calf Raise |
 | Stretching mat (cool-down) | Standing Forward Fold, Standing Quad Stretch, Standing Calf Stretch, Chest Opener, Overhead Triceps Stretch, Kneeling Hip Flexor Stretch, Butterfly Stretch, Cobra Stretch, Child's Pose |
+| Quiet corner (mindfulness) | Meditation |
 
 ## Considered exclusions (the "most gyms" line)