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/Bodyweight Squat/visual.svg

@@ -1,13 +1,31 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 180" fill="none">
   <title>Bodyweight Squat</title>
+  <defs>
+    <linearGradient id="grad-leg_l-0" gradientUnits="userSpaceOnUse" x1="154.3" y1="120.3" x2="184.4" y2="131.7"><stop offset="0" stop-color="#6cc2b8"/><stop offset="1" stop-color="#86cfc5"/></linearGradient>
+    <linearGradient id="grad-leg_r-2" gradientUnits="userSpaceOnUse" x1="160.0" y1="149.6" x2="166.9" y2="152.9"><stop offset="0" stop-color="#0d9488"/><stop offset="1" stop-color="#199a8e"/></linearGradient>
+  </defs>
   <path d="M 141.8 157.9 L 232.3 157.9 L 232.3 150.6 L 141.8 150.6 Z" fill="none" stroke="#b9bec9" stroke-width="2.1" stroke-linejoin="round"/>
-  <path id="leg_l" d="M 154.3 120.3 L 184.4 131.7 L 162.8 149.3 L 169.6 152.9" stroke="#86cfc5" stroke-width="3.5" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="arm_l" d="M 182.3 68.1 L 203.3 67.4 L 223.9 63.8" stroke="#a9afba" stroke-width="3.5" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="leg_r" d="M 150.2 120.7 L 180.6 131.0 L 160.0 149.6 L 166.9 152.9" stroke="#0d9488" stroke-width="4.2" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="leg_l">
+    <path d="M 154.3 120.3 L 184.4 131.7" stroke="url(#grad-leg_l-0)" stroke-width="3.57578" stroke-linecap="round"/>
+    <path d="M 184.4 131.7 L 162.8 149.3" stroke="#86cfc5" stroke-width="3.5" stroke-linecap="round"/>
+    <path d="M 162.8 149.3 L 169.6 152.9" stroke="#86cfc5" stroke-width="3.5" stroke-linecap="round"/>
+  </g>
+  <g id="arm_l">
+    <path d="M 182.3 68.1 L 203.3 67.4" stroke="#a9afba" stroke-width="3.5" stroke-linecap="round"/>
+    <path d="M 203.3 67.4 L 223.9 63.8" stroke="#a9afba" stroke-width="3.5" stroke-linecap="round"/>
+  </g>
+  <g id="leg_r">
+    <path d="M 150.2 120.7 L 180.6 131.0" stroke="#0d9488" stroke-width="4.2" stroke-linecap="round"/>
+    <path d="M 180.6 131.0 L 160.0 149.6" stroke="#0d9488" stroke-width="4.2" stroke-linecap="round"/>
+    <path d="M 160.0 149.6 L 166.9 152.9" stroke="url(#grad-leg_r-2)" stroke-width="4.16575" stroke-linecap="round"/>
+  </g>
   <path id="girdle" d="M 182.3 68.1 L 178.1 68.1 L 178.1 69.4" stroke="#3a3f4b" stroke-width="3.5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="pelvisBar" d="M 154.3 120.3 L 150.2 119.8 L 150.2 120.7" stroke="#3a3f4b" stroke-width="3.5" stroke-linecap="round" stroke-linejoin="round"/>
   <path id="spine" d="M 150.2 119.8 Q 166.3 94.3 178.1 68.1" stroke="#3a3f4b" stroke-width="4.2" stroke-linecap="round" stroke-linejoin="round"/>
-  <path id="arm_r" d="M 178.1 69.4 L 199.1 68.7 L 219.8 65.1" stroke="#3a3f4b" stroke-width="4.2" stroke-linecap="round" stroke-linejoin="round"/>
+  <g id="arm_r">
+    <path d="M 178.1 69.4 L 199.1 68.7" stroke="#3a3f4b" stroke-width="4.2" stroke-linecap="round"/>
+    <path d="M 199.1 68.7 L 219.8 65.1" stroke="#3a3f4b" stroke-width="4.2" stroke-linecap="round"/>
+  </g>
   <circle id="head" cx="185.3" cy="56.3" r="7.0" fill="white" stroke="#3a3f4b" stroke-width="4.2"/>
   <line id="nose" x1="192.3" y1="57.1" x2="197.2" y2="57.7" stroke="#3a3f4b" stroke-width="2.8" stroke-linecap="round"/>
   <g font-family="-apple-system, Helvetica, sans-serif" font-size="11" fill="#6b7180">