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>