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/Model/Entities.swift

@@ -64,12 +64,13 @@ final class Exercise {
     var durationTotalSeconds: Int = 0
     var weightLastUpdated: Date?
     var weightReminderTimeIntervalWeeks: Int = 2
+    var categoryRaw: Int = ExerciseCategory.main.rawValue
 
     var split: Split?
 
     init(id: String, name: String, order: Int, sets: Int, reps: Int, weight: Int,
          loadType: Int, durationTotalSeconds: Int, weightLastUpdated: Date?,
-         weightReminderTimeIntervalWeeks: Int) {
+         weightReminderTimeIntervalWeeks: Int, categoryRaw: Int = ExerciseCategory.main.rawValue) {
         self.id = id
         self.name = name
         self.order = order
@@ -80,6 +81,7 @@ final class Exercise {
         self.durationTotalSeconds = durationTotalSeconds
         self.weightLastUpdated = weightLastUpdated
         self.weightReminderTimeIntervalWeeks = weightReminderTimeIntervalWeeks
+        self.categoryRaw = categoryRaw
     }
 
     var loadTypeEnum: LoadType {
@@ -87,6 +89,27 @@ final class Exercise {
         set { loadType = newValue.rawValue }
     }
 
+    var categoryEnum: ExerciseCategory {
+        get { ExerciseCategory(rawValue: categoryRaw) ?? .main }
+        set { categoryRaw = newValue.rawValue }
+    }
+
+    /// One-line plan summary for list rows — duration exercises show their hold time
+    /// ("3 × 45 sec"), unloaded ones drop the weight ("3 × 12 reps"), weighted ones
+    /// keep the full "3 × 10 × 40 lb".
+    func planSummary(weightUnit: WeightUnit) -> String {
+        switch loadTypeEnum {
+        case .duration:
+            let m = durationMinutes, s = durationSeconds
+            let hold = m > 0 && s > 0 ? "\(m)m \(s)s" : (m > 0 ? "\(m) min" : "\(s) sec")
+            return "\(sets) × \(hold)"
+        case .none:
+            return "\(sets) × \(reps) reps"
+        case .weight:
+            return "\(sets) × \(reps) × \(weightUnit.format(weight))"
+        }
+    }
+
     /// Minutes component of the total duration (for min:sec pickers).
     var durationMinutes: Int {
         get { durationTotalSeconds / 60 }