Add Warm-Up and Stretching activity types

Adds WorkoutActivityType.warmUp (HealthKit .preparationAndRecovery) and
.stretching (.flexibility), and retags the six starter splits that were all
mislabeled as Functional Strength:

- Warm-Up:    Upper Body Warm-Up, Lower Body Warm-Up, Morning Wake-Up
- Stretching: Morning Mobility, Full Body Stretch, Evening Stretch

The split editor's activity picker surfaces them automatically (CaseIterable).
Older app versions decode the new raw values as the default type — additive and
not schema-gated, so no quarantine.

Exercise Library/Bird Dog/visual.svg

@@ -1,13 +1,34 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
   <title>Bird Dog</title>
+  <defs>
+    <linearGradient id="grad-leg_r-0" gradientUnits="userSpaceOnUse" x1="195.9" y1="106.8" x2="240.3" y2="95.0"><stop offset="0" stop-color="#86cfc5"/><stop offset="1" stop-color="#72c5bb"/></linearGradient>
+    <linearGradient id="grad-leg_r-1" gradientUnits="userSpaceOnUse" x1="240.3" y1="95.0" x2="279.0" y2="84.8"><stop offset="0" stop-color="#72c5bb"/><stop offset="1" stop-color="#58b8ae"/></linearGradient>
+    <linearGradient id="grad-leg_r-2" gradientUnits="userSpaceOnUse" x1="279.0" y1="84.8" x2="286.0" y2="93.1"><stop offset="0" stop-color="#58b8ae"/><stop offset="1" stop-color="#6dc3b8"/></linearGradient>
+    <linearGradient id="grad-leg_l-0" gradientUnits="userSpaceOnUse" x1="190.0" y1="107.2" x2="195.6" y2="152.2"><stop offset="0" stop-color="#0d9488"/><stop offset="1" stop-color="#3aaa9f"/></linearGradient>
+    <linearGradient id="grad-leg_l-2" gradientUnits="userSpaceOnUse" x1="235.6" y1="152.2" x2="244.6" y2="158.4"><stop offset="0" stop-color="#3aaa9f"/><stop offset="1" stop-color="#4ab2a7"/></linearGradient>
+  </defs>
   <path d="M 37.3 160.4 L 298.0 160.4 L 298.0 150.0 L 37.3 150.0 Z" fill="none" stroke="#b9bec9" stroke-width="3" stroke-linejoin="round"/>
-  <path id="arm_r" d="M 112.0 93.0 L 115.9 122.2 L 111.0 151.4" stroke="#86cfc5" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="leg_r" d="M 195.9 106.8 L 240.3 95.0 L 279.0 84.8 L 286.0 93.1" stroke="#86cfc5" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="leg_l" d="M 190.0 107.2 L 195.6 152.2 L 235.6 152.2 L 244.6 158.4" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="arm_r">
+    <path d="M 112.0 93.0 L 115.9 122.2" stroke="#86cfc5" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 115.9 122.2 L 111.0 151.4" stroke="#86cfc5" stroke-width="5" stroke-linecap="round"/>
+  </g>
+  <g id="leg_r">
+    <path d="M 195.9 106.8 L 240.3 95.0" stroke="url(#grad-leg_r-0)" stroke-width="5.0833" stroke-linecap="round"/>
+    <path d="M 240.3 95.0 L 279.0 84.8" stroke="url(#grad-leg_r-1)" stroke-width="5.27526" stroke-linecap="round"/>
+    <path d="M 279.0 84.8 L 286.0 93.1" stroke="url(#grad-leg_r-2)" stroke-width="5.29548" stroke-linecap="round"/>
+  </g>
+  <g id="leg_l">
+    <path d="M 190.0 107.2 L 195.6 152.2" stroke="url(#grad-leg_l-0)" stroke-width="5.81247" stroke-linecap="round"/>
+    <path d="M 195.6 152.2 L 235.6 152.2" stroke="#3aaa9f" stroke-width="5.62495" stroke-linecap="round"/>
+    <path d="M 235.6 152.2 L 244.6 158.4" stroke="url(#grad-leg_l-2)" stroke-width="5.55873" stroke-linecap="round"/>
+  </g>
   <path id="girdle" d="M 106.0 94.8 L 106.0 92.9 L 112.0 93.0" stroke="#3a3f4b" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="pelvisBar" d="M 190.0 107.2 L 190.0 106.0 L 195.9 106.8" stroke="#3a3f4b" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="spine" d="M 190.0 106.0 Q 147.0 99.3 106.0 92.9" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="arm_l" d="M 106.0 94.8 L 77.7 85.2 L 49.3 75.6" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="arm_l">
+    <path d="M 106.0 94.8 L 77.7 85.2" stroke="#0d9488" stroke-width="6" stroke-linecap="round"/>
+    <path d="M 77.7 85.2 L 49.3 75.6" stroke="#0d9488" stroke-width="6" stroke-linecap="round"/>
+  </g>
   <circle id="head" cx="86.2" cy="95.3" r="10" fill="white" stroke="#3a3f4b" stroke-width="6"/>
   <line id="nose" x1="76.5" y1="97.9" x2="69.8" y2="99.6" stroke="#3a3f4b" stroke-width="4" stroke-linecap="round"/>
   <g font-family="-apple-system, Helvetica, sans-serif" font-size="11" fill="#6b7180">