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/Views/Exercises/ExerciseAddEditView.swift

@@ -33,6 +33,7 @@ struct ExerciseAddEditView: View {
     @State private var sets: Int
     @State private var weightReminderWeeks: Int
     @State private var weightLastUpdated: Date?
+    @State private var category: ExerciseCategory
     @AppStorage("weightUnit") private var weightUnit: WeightUnit = .lb
 
     init(exercise: Exercise, split: Split) {
@@ -51,6 +52,7 @@ struct ExerciseAddEditView: View {
         _sets = State(initialValue: exercise.sets)
         _weightReminderWeeks = State(initialValue: exercise.weightReminderTimeIntervalWeeks)
         _weightLastUpdated = State(initialValue: exercise.weightLastUpdated)
+        _category = State(initialValue: exercise.categoryEnum)
     }
 
     var body: some View {
@@ -98,6 +100,19 @@ struct ExerciseAddEditView: View {
                     }
                 }
 
+                Section(
+                    header: Text("Category"),
+                    footer: Text("The split screen groups its exercises by category, with the warm-up listed first.")
+                ) {
+                    Picker("", selection: $category) {
+                        ForEach(ExerciseCategory.displayOrder, id: \.self) { cat in
+                            Text(cat.displayName)
+                                .tag(cat)
+                        }
+                    }
+                    .pickerStyle(.segmented)
+                }
+
                 Section(
                     header: Text("Load Type"),
                     footer: Text("For bodyweight exercises choose None. For resistance or weight training select Weight. For exercises that are time oriented (like plank or meditation) select Time.")
@@ -204,6 +219,7 @@ struct ExerciseAddEditView: View {
             doc.exercises[idx].durationSeconds = durationSecs
             doc.exercises[idx].weightLastUpdated = updatedWeightDate
             doc.exercises[idx].weightReminderWeeks = weightReminderWeeks
+            doc.exercises[idx].category = category.rawValue
         }
         doc.updatedAt = Date()
         Task { await sync.save(split: doc) }