Add the exercise reference library, animated exercise figures, and exercise categories

Exercise Library/ holds per-exercise reference docs (setup, cues,
mistakes, progressions) with SVG visuals and a Python-rendered motion
pipeline; Workouts/ExerciseFigure renders the bundled *.motion.json
rigs as animated stick figures on the exercise screen. Exercises gain
a warm-up/main-circuit category, timed exercises display hold time via
planSummary, and a completed exercise reopens to a check screen instead
of its timers.

Shared/Persistence/WorkoutsModelContainer.swift

@@ -7,7 +7,8 @@ import SwiftData
 enum WorkoutsModelContainer {
     /// Bump whenever the cache schema changes — wipes and rebuilds from files.
     /// 2: added health-metric columns to `Workout` and `activityTypeRaw` to `Split`.
-    static let currentSchemaVersion = 2
+    /// 3: added `categoryRaw` to `Exercise`.
+    static let currentSchemaVersion = 3
     private static let schemaVersionKey = "Workouts.persistenceSchemaVersion"
     private static let identityTokenKey = "Workouts.iCloudIdentityToken"