feat(pose_3d): named poses GET/PUT/DELETE

Adds CRUD for named wrist poses persisted in config.yaml under
pose_3d.named_poses. PUT validates the name against ^[A-Za-z0-9_-]{1,40}$
and normalizes the quaternion. DELETE returns 404 if the pose is missing.

Bypasses update_config's deep-merge for wholesale named_poses replacement
(deep-merge cannot remove nested keys) via a small helper that mutates
the in-memory singleton then persists with an empty patch.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_pose_3d_routes.py

@@ -117,3 +117,46 @@ def test_apply_normalizes_quaternion_before_forwarding():
         q = captured["quaternion"]
         norm = sum(x*x for x in q) ** 0.5
         assert abs(norm - 1.0) < 1e-6
+
+
+def test_put_pose_persists_in_config():
+    payload = {
+        "side": "right",
+        "position": [0.30, -0.20, 0.30],
+        "quaternion": [0, 0, 0, 1],
+        "note": "test pose",
+    }
+    r = client.put("/api/pose_3d/poses/test1", json=payload)
+    assert r.status_code == 200
+    body = r.json()
+    assert body["pose"]["side"] == "right"
+    assert body["pose"]["note"] == "test pose"
+    # Verifica che sia anche in GET /poses
+    r2 = client.get("/api/pose_3d/poses")
+    assert "test1" in r2.json()
+
+
+def test_put_pose_422_bad_name():
+    r = client.put("/api/pose_3d/poses/with spaces!", json={
+        "side": "right", "position": [0,0,0], "quaternion": [0,0,0,1],
+    })
+    assert r.status_code == 422
+    assert "name" in r.json()["detail"].lower()
+
+
+def test_delete_pose_removes_it():
+    # prima salva
+    client.put("/api/pose_3d/poses/todelete", json={
+        "side": "left", "position": [0,0,0], "quaternion": [0,0,0,1],
+    })
+    # poi cancella
+    r = client.delete("/api/pose_3d/poses/todelete")
+    assert r.status_code == 200
+    # verifica non presente
+    r2 = client.get("/api/pose_3d/poses")
+    assert "todelete" not in r2.json()
+
+
+def test_delete_pose_404_when_missing():
+    r = client.delete("/api/pose_3d/poses/nonexistent")
+    assert r.status_code == 404