By: Tom Sydney Kerckhove <syd@cs-syd.eu>
Show a coloured character diff for similar-attachment hints When an attachment file does not exist, the CE_MISSING_ATTACHMENT hint now renders each suggested file name as a character-level diff against the name that was typed, using fast-myers-diff and safe-coloured-text. Only characters that are actually part of the candidate path are shown, so the rendered text is always a real path. Characters the candidate has in addition to the typed name are coloured red, and unchanged characters are coloured explicitly so the whole suggestion stays one colour regardless of where the differences fall. Add a many-similar-attachments scenario exercising substitution, insertion, extension change, deletion, and reordering. The check spec now recurses into subdirectories so the scenario can isolate its candidate files in their own directory.