Rename device frames to remove ASCII double-quote from filenames

[jonnyjackson26]

There are 18 frame PNGs whose basenames contained an ASCII double-quote ("):

iPad Air 11"/13" M2 in all four colors, iMac 24" Silver, and MacBook Air 13" 4th Gen Midnight

These cannot be materialized on Windows because the OS reserves <>:"|?* and rejects any path containing them. Two user-visible failure paths result:

• git clone aborts mid-checkout with error: invalid path 'src/koubou/frames/MacBook Air 13" - 4th Gen - Midnight.png' and leaves the working tree empty.
• kou setup-frames (and the implicit download triggered by kou generate) fails partway through tarfile.extract with [Errno 22] Invalid argument, after which the cleanup path in frame_manager.download_frames wipes the partial cache.

FIX:
Drop the double-quote entirely so the names match the bare-number convention already used elsewhere in the directory (iPad Pro 11 - M4 - ..., iPad Pro 13 - M4 - ..., MacBook Pro 2021 14). No content changes -- the blob bytes are identical, only the path differs.

Also updates README.md, CHANGELOG.md, and
skills/koubou/yaml-reference.md where the same device names appeared in user-facing reference text.

Note: users with an existing YAML referencing the old name (e.g. device: iPad Air 13" - M2 - Space Gray - Portrait) will need to drop the " from their config. A back-compat alias map in _load_frame_image / _get_frame_info can be added in a follow-up if the maintainer wants to avoid the breaking change.

[bitomule]

Thank you!! I'll merge it and update the changelog to reflect the breaking change.