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/Reverse Crunch/frames/frame-2.svg

@@ -1,13 +1,30 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
   <title>Reverse Crunch</title>
+  <defs>
+    <linearGradient id="grad-leg_r-0" gradientUnits="userSpaceOnUse" x1="166.0" y1="137.2" x2="146.6" y2="96.2"><stop offset="0" stop-color="#5c616d"/><stop offset="1" stop-color="#3a3f4b"/></linearGradient>
+  </defs>
   <path d="M 40.6 160.9 L 223.3 160.9 L 223.3 150.5 L 40.6 150.5 Z" fill="none" stroke="#b9bec9" stroke-width="3" stroke-linejoin="round"/>
-  <path id="arm_l" d="M 88.5 143.4 L 118.5 144.4 L 148.5 145.5" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="leg_l" d="M 171.9 136.8 L 152.5 95.7 L 191.9 102.5 L 193.8 91.9" stroke="#a9afba" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="arm_l">
+    <path d="M 88.5 143.4 L 118.5 144.4" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 118.5 144.4 L 148.5 145.5" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+  </g>
+  <g id="leg_l">
+    <path d="M 171.9 136.8 L 152.5 95.7" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 152.5 95.7 L 191.9 102.5" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+    <path d="M 191.9 102.5 L 193.8 91.9" stroke="#a9afba" stroke-width="5" stroke-linecap="round"/>
+  </g>
   <path id="girdle" d="M 88.5 143.4 L 82.6 143.4 L 82.6 145.3" stroke="#0d9488" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="pelvisBar" d="M 171.9 136.8 L 166.0 136.0 L 166.0 137.2" stroke="#0d9488" stroke-width="5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="spine" d="M 166.0 136.0 Q 124.6 154.2 82.6 143.4" stroke="#0d9488" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="arm_r" d="M 82.6 145.3 L 112.6 146.3 L 142.6 147.3" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="leg_r" d="M 166.0 137.2 L 146.6 96.2 L 186.0 103.0 L 187.9 92.3" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="arm_r">
+    <path d="M 82.6 145.3 L 112.6 146.3" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round"/>
+    <path d="M 112.6 146.3 L 142.6 147.3" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round"/>
+  </g>
+  <g id="leg_r">
+    <path d="M 166.0 137.2 L 146.6 96.2" stroke="url(#grad-leg_r-0)" stroke-width="5.84652" stroke-linecap="round"/>
+    <path d="M 146.6 96.2 L 186.0 103.0" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round"/>
+    <path d="M 186.0 103.0 L 187.9 92.3" stroke="#3a3f4b" stroke-width="6" stroke-linecap="round"/>
+  </g>
   <circle id="head" cx="62.6" cy="144.0" r="10" fill="white" stroke="#3a3f4b" stroke-width="6"/>
   <line id="nose" x1="62.6" y1="134.0" x2="62.6" y2="127.1" stroke="#3a3f4b" stroke-width="4" stroke-linecap="round"/>
   <g font-family="-apple-system, Helvetica, sans-serif" font-size="11" fill="#6b7180">