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/Butterfly Stretch/frames/frame-2.svg

@@ -1,13 +1,32 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
   <title>Butterfly Stretch</title>
+  <defs>
+    <linearGradient id="grad-leg_l-2" gradientUnits="userSpaceOnUse" x1="193.5" y1="156.8" x2="202.9" y2="161.8"><stop offset="0" stop-color="#86cfc5"/><stop offset="1" stop-color="#48b1a6"/></linearGradient>
+    <linearGradient id="grad-leg_r-0" gradientUnits="userSpaceOnUse" x1="154.5" y1="118.7" x2="149.2" y2="133.4"><stop offset="0" stop-color="#86cfc5"/><stop offset="1" stop-color="#0d9488"/></linearGradient>
+    <linearGradient id="grad-arm_r-0" gradientUnits="userSpaceOnUse" x1="185.5" y1="65.8" x2="183.4" y2="94.7"><stop offset="0" stop-color="#686d79"/><stop offset="1" stop-color="#3a3f4b"/></linearGradient>
+  </defs>
   <path d="M 122.3 155.5 L 178.0 167.9 L 225.2 161.5 L 169.6 149.1 Z" fill="none" stroke="#b9bec9" stroke-width="3" stroke-linejoin="round"/>
-  <path id="leg_l" d="M 169.2 118.5 L 214.3 126.3 L 193.5 156.8 L 202.9 161.8" stroke="#86cfc5" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="leg_l">
+    <path d="M 169.2 118.5 L 214.3 126.3" stroke="#86cfc5" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 214.3 126.3 L 193.5 156.8" stroke="#86cfc5" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 193.5 156.8 L 202.9 161.8" stroke="url(#grad-leg_l-2)" stroke-width="5.25531" stroke-linecap="round"/>
+  </g>
   <path id="girdle" d="M 206.5 64.6 L 194.2 64.6 L 185.5 65.8" stroke="#3a3f4b" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="pelvisBar" d="M 169.2 118.5 L 160.0 118.0 L 154.5 118.7" stroke="#3a3f4b" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="spine" d="M 160.0 118.0 Q 169.4 77.2 194.2 64.6" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="leg_r" d="M 154.5 118.7 L 149.2 133.4 L 174.1 157.7 L 175.2 163.9" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="arm_l" d="M 206.5 64.6 L 205.2 94.4 L 203.2 124.1" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="arm_r" d="M 185.5 65.8 L 183.4 94.7 L 180.7 123.7" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="leg_r">
+    <path d="M 154.5 118.7 L 149.2 133.4" stroke="url(#grad-leg_r-0)" stroke-width="5.5" stroke-linecap="round"/>
+    <path d="M 149.2 133.4 L 174.1 157.7" stroke="#0d9488" stroke-width="6" stroke-linecap="round"/>
+    <path d="M 174.1 157.7 L 175.2 163.9" stroke="#0d9488" stroke-width="6" stroke-linecap="round"/>
+  </g>
+  <g id="arm_l">
+    <path d="M 206.5 64.6 L 205.2 94.4" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 205.2 94.4 L 204.4 124.0" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+  </g>
+  <g id="arm_r">
+    <path d="M 185.5 65.8 L 183.4 94.7" stroke="url(#grad-arm_r-0)" stroke-width="5.79336" stroke-linecap="round"/>
+    <path d="M 183.4 94.7 L 181.7 123.5" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round"/>
+  </g>
   <circle id="head" cx="205.6" cy="59.8" r="10" fill="white" stroke="#3a3f4b" stroke-width="6"/>
   <line id="nose" x1="209.6" y1="68.9" x2="212.3" y2="74.9" stroke="#3a3f4b" stroke-width="4" stroke-linecap="round"/>
   <g font-family="-apple-system, Helvetica, sans-serif" font-size="11" fill="#6b7180">