Replace `[zrdt-269](https://github.com/umitkavala/zere-synth/commit/018b959)` with the bare commit hash `zrdt-269 (commit 018b959)`. The previous link pointed at a private GitHub repo which 404s for anonymous HF viewers and leaks the internal URL. Card content is otherwise unchanged.
docs: add Pose convention section (zrdt-270 Option B) (#2)
