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/Side Plank/frames/frame-2.svg

@@ -1,13 +1,31 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
   <title>Side Plank</title>
+  <defs>
+    <linearGradient id="grad-arm_r-1" gradientUnits="userSpaceOnUse" x1="111.2" y1="96.9" x2="126.2" y2="71.4"><stop offset="0" stop-color="#a9afba"/><stop offset="1" stop-color="#858b96"/></linearGradient>
+    <linearGradient id="grad-arm_l-0" gradientUnits="userSpaceOnUse" x1="90.3" y1="124.4" x2="90.0" y2="153.9"><stop offset="0" stop-color="#3a3f4b"/><stop offset="1" stop-color="#464b57"/></linearGradient>
+  </defs>
   <path d="M 48.0 160.9 L 277.9 160.9 L 277.9 150.5 L 48.0 150.5 Z" fill="none" stroke="#b9bec9" stroke-width="3" stroke-linejoin="round"/>
-  <path id="leg_r" d="M 179.9 137.8 L 225.2 145.6 L 264.6 152.5 L 262.7 163.1" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="arm_r" d="M 96.2 122.5 L 111.2 96.9 L 126.2 71.4" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="leg_r">
+    <path d="M 179.9 137.8 L 225.2 145.6" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 225.2 145.6 L 264.6 152.5" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 264.6 152.5 L 262.7 163.1" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+  </g>
+  <g id="arm_r">
+    <path d="M 96.2 122.5 L 111.2 96.9" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 111.2 96.9 L 126.2 71.4" stroke="url(#grad-arm_r-1)" stroke-width="5.16015" stroke-linecap="round"/>
+  </g>
   <path id="girdle" d="M 90.3 124.4 L 90.3 122.5 L 96.2 122.5" stroke="#0d9488" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="pelvisBar" d="M 174.0 138.2 L 174.0 137.0 L 179.9 137.8" stroke="#0d9488" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="spine" d="M 174.0 137.0 Q 131.2 129.6 90.3 122.5" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="leg_l" d="M 174.0 138.2 L 219.3 146.1 L 258.7 152.9 L 256.8 163.6" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="arm_l" d="M 90.3 124.4 L 90.0 153.9 L 60.0 153.7" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="leg_l">
+    <path d="M 174.0 138.2 L 219.3 146.1" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round"/>
+    <path d="M 219.3 146.1 L 258.7 152.9" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round"/>
+    <path d="M 258.7 152.9 L 256.8 163.6" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round"/>
+  </g>
+  <g id="arm_l">
+    <path d="M 90.3 124.4 L 90.0 153.9" stroke="url(#grad-arm_l-0)" stroke-width="5.94606" stroke-linecap="round"/>
+    <path d="M 90.0 153.9 L 60.0 153.7" stroke="#464b57" stroke-width="5.89372" stroke-linecap="round"/>
+  </g>
   <circle id="head" cx="70.6" cy="119.0" r="10" fill="white" stroke="#3a3f4b" stroke-width="6"/>
   <line id="nose" x1="60.6" y1="119.0" x2="53.6" y2="119.0" stroke="#3a3f4b" stroke-width="4" stroke-linecap="round"/>
   <g font-family="-apple-system, Helvetica, sans-serif" font-size="11" fill="#6b7180">