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/Sync/WriteBacklog.swift

@@ -13,9 +13,21 @@ import Foundation
 /// supersede checks key on it, newer wins.
 struct PendingWrite: Codable, Sendable {
     enum Payload: Codable, Sendable {
-        case split(SplitDocument)
+        case routine(RoutineDocument)
         case workout(WorkoutDocument)
+        case schedule(ScheduleDocument)
         case delete(id: String, kind: String, livePath: String)
+
+        // PINNED KEY: the case was renamed `.split` → `.routine`, but its persisted
+        // JSON key stays `"split"` so a `PendingWrites.json` sidecar written by a
+        // previous run still decodes. `workout` / `schedule` / `delete` keep their
+        // default keys.
+        enum CodingKeys: String, CodingKey {
+            case routine = "split"
+            case workout
+            case schedule
+            case delete
+        }
     }
 
     var payload: Payload
@@ -36,8 +48,9 @@ struct PendingWrite: Codable, Sendable {
 
     var documentID: String {
         switch payload {
-        case .split(let doc): doc.id
+        case .routine(let doc): doc.id
         case .workout(let doc): doc.id
+        case .schedule(let doc): doc.id
         case .delete(let id, _, _): id
         }
     }
@@ -45,8 +58,9 @@ struct PendingWrite: Codable, Sendable {
     /// Where a successful write lands; nil for deletes (they only remove).
     var targetPath: String? {
         switch payload {
-        case .split(let doc): doc.relativePath
+        case .routine(let doc): doc.relativePath
         case .workout(let doc): doc.relativePath
+        case .schedule(let doc): doc.relativePath
         case .delete: nil
         }
     }