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.

Workouts/Screenshots/ScreenshotRootView.swift

@@ -20,6 +20,7 @@ struct ScreenshotRootView: View {
         content
             .environment(services)
             .environment(services.syncEngine)
+            .environment(services.liveRunState)
             .modelContainer(services.container)
     }