A .dng could not be attached at all: browsers label it as TIFF (rejected as an
unsupported image), as PNG/JPEG (sent down the image compression path), or with
an empty/octet-stream type. DNG originals now always classify as generic files,
captioned DNG pastes are claimed, and the staged record carries
image/x-adobe-dng so downstream readers (isImageAttachment, the provider image
byte budget) never re-read a mislabelled DNG as a picture. Only DNG, not every
RAW format.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>