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/Cat-Cow/frames/frame-1.svg

@@ -0,0 +1,17 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
+  <title>Cat-Cow</title>
+  <line x1="16" y1="156" x2="304" y2="156" stroke="#b9bec9" stroke-width="3" stroke-linecap="round"/>
+  <path id="arm_l" d="M 115.4 96.2 L 121.0 125.7 L 111.0 154.0" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="leg_l" d="M 196.0 108.0 L 201.6 153.7 L 241.6 153.7" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="spine" d="M 190.0 106.0 Q 145.2 123.9 109.4 94.2" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="arm_r" d="M 109.4 94.2 L 115.0 123.7 L 105.0 152.0" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="leg_r" d="M 190.0 106.0 L 195.6 151.7 L 235.6 151.7" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <circle id="head" cx="89.4" cy="96.0" r="10" fill="white" stroke="#3a3f4b" stroke-width="6"/>
+  <line id="nose" x1="79.8" y1="93.2" x2="73.1" y2="91.3" stroke="#3a3f4b" stroke-width="4" stroke-linecap="round"/>
+  <g font-family="-apple-system, Helvetica, sans-serif" font-size="11" fill="#6b7180">
+    <line x1="242" y1="16" x2="258" y2="16" stroke="#3a3f4b" stroke-width="4" stroke-linecap="round"/>
+    <text x="264" y="20">R</text>
+    <line x1="282" y1="16" x2="298" y2="16" stroke="#a9afba" stroke-width="4" stroke-linecap="round"/>
+    <text x="304" y="20">L</text>
+  </g>
+</svg>

Exercise Library/Cat-Cow/frames/frame-2.svg

@@ -0,0 +1,17 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
+  <title>Cat-Cow</title>
+  <line x1="16" y1="156" x2="304" y2="156" stroke="#b9bec9" stroke-width="3" stroke-linecap="round"/>
+  <path id="arm_l" d="M 115.9 98.6 L 124.6 127.3 L 111.0 154.0" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="leg_l" d="M 196.0 108.0 L 201.6 153.7 L 241.6 153.7" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="spine" d="M 190.0 106.0 Q 152.1 74.4 109.9 96.6" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="arm_r" d="M 109.9 96.6 L 118.6 125.3 L 105.0 152.0" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="leg_r" d="M 190.0 106.0 L 195.6 151.7 L 235.6 151.7" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <circle id="head" cx="93.6" cy="108.0" r="10" fill="white" stroke="#3a3f4b" stroke-width="6"/>
+  <line id="nose" x1="86.5" y1="115.1" x2="81.5" y2="120.1" stroke="#3a3f4b" stroke-width="4" stroke-linecap="round"/>
+  <g font-family="-apple-system, Helvetica, sans-serif" font-size="11" fill="#6b7180">
+    <line x1="242" y1="16" x2="258" y2="16" stroke="#3a3f4b" stroke-width="4" stroke-linecap="round"/>
+    <text x="264" y="20">R</text>
+    <line x1="282" y1="16" x2="298" y2="16" stroke="#a9afba" stroke-width="4" stroke-linecap="round"/>
+    <text x="304" y="20">L</text>
+  </g>
+</svg>