feat: desk standup stretch pose for office ergonomics (closes #52)

data/poses/desk_standup_stretch.json

@@ -0,0 +1,40 @@
+{
+  "id": "desk_standup_stretch",
+  "name": "Desk Standup Stretch",
+  "standing": true,
+  "tags": [
+    "indoor",
+    "office",
+    "ergonomic",
+    "stretch",
+    "casual",
+    "daylight"
+  ],
+  "tips": [
+    "Stand tall, feet shoulder-width apart",
+    "Arms overhead, interlace fingers, palms up",
+    "Gentle backward lean, avoid over-arching lower back",
+    "Hold 15-30 seconds, breathe deeply"
+  ],
+  "camera_cues": [
+    "full body, eye level",
+    "office environment visible in background",
+    "natural window light or soft overhead",
+    "three-quarter angle shows stretch extension"
+  ],
+  "joints": {
+    "nose": [0.5, 0.08, 0.0],
+    "l_shoulder": [0.42, 0.22, 0.0],
+    "r_shoulder": [0.58, 0.22, 0.0],
+    "l_elbow": [0.38, 0.18, 0.0],
+    "r_elbow": [0.62, 0.18, 0.0],
+    "l_wrist": [0.44, 0.12, 0.0],
+    "r_wrist": [0.56, 0.12, 0.0],
+    "l_hip": [0.45, 0.52, 0.0],
+    "r_hip": [0.55, 0.52, 0.0],
+    "l_knee": [0.45, 0.7, 0.0],
+    "r_knee": [0.55, 0.7, 0.0],
+    "l_ankle": [0.45, 0.9, 0.0],
+    "r_ankle": [0.55, 0.9, 0.0]
+  }
+}