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.

Exercise Library/body.json

@@ -0,0 +1,24 @@
+{
+  "neutral": {
+    "headR": 10,
+    "neck": 20,
+    "spine1": 43,
+    "spine2": 42,
+    "upperArm": 30,
+    "foreArm": 30,
+    "thigh": 46,
+    "shin": 40,
+    "leftOffset": [6, 2]
+  },
+  "female": {
+    "headR": 9,
+    "neck": 19,
+    "spine1": 40,
+    "spine2": 39,
+    "upperArm": 27,
+    "foreArm": 27,
+    "thigh": 47,
+    "shin": 41,
+    "leftOffset": [6, 2]
+  }
+}