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/Side Plank/frames/frame-1.svg

@@ -0,0 +1,17 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
+  <title>Side Plank</title>
+  <line x1="16" y1="156" x2="304" y2="156" stroke="#b9bec9" stroke-width="3" stroke-linecap="round"/>
+  <path id="arm_l" d="M 99.2 125.7 L 127.4 136.0 L 156.3 143.8" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="leg_l" d="M 180.0 152.0 L 226.0 152.8 L 266.0 153.5" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="spine" d="M 174.0 150.0 Q 132.6 136.6 93.2 123.7" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="arm_r" d="M 93.2 123.7 L 90.0 153.6 L 60.0 152.0" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="leg_r" d="M 174.0 150.0 L 220.0 150.8 L 260.0 151.5" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <circle id="head" cx="74.1" cy="117.6" r="10" fill="white" stroke="#3a3f4b" stroke-width="6"/>
+  <line id="nose" x1="64.2" y1="116.7" x2="57.2" y2="116.1" 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>

Exercise Library/Side Plank/frames/frame-2.svg

@@ -0,0 +1,17 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
+  <title>Side Plank</title>
+  <line x1="16" y1="156" x2="304" y2="156" stroke="#b9bec9" stroke-width="3" stroke-linecap="round"/>
+  <path id="arm_l" d="M 96.3 124.2 L 101.5 94.7 L 106.7 65.2" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="leg_l" d="M 180.0 139.0 L 225.3 147.0 L 264.7 153.9" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="spine" d="M 174.0 137.0 Q 131.2 129.4 90.3 122.2" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="arm_r" d="M 90.3 122.2 L 90.0 152.2 L 60.0 152.0" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <path id="leg_r" d="M 174.0 137.0 L 219.3 145.0 L 258.7 151.9" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <circle id="head" cx="70.6" cy="118.8" r="10" fill="white" stroke="#3a3f4b" stroke-width="6"/>
+  <line id="nose" x1="60.6" y1="118.8" x2="53.6" y2="118.8" 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>