set(), end() and move_cursor() used the byte length of the input as the
cursor bound while append/backspace/delete/clear_* index a grapheme table.
Any non-ASCII input (æøå, emoji) followed by End or typing past the end
indexed out of bounds and, with panic = "abort" in release, killed wldash.
While here:
- clamp Up so the selection can't run past the last row (every widget now
reports its row count), and make mouse selection underflow-safe
- strip all desktop-entry field codes from Exec (%i %c %k ... and %% -> %),
not just %f/%F/%u/%U
- report a failed spawn instead of panicking
- size the highlight colour table by chars, matching the drawing code
Adds unit tests for the prompt and the field-code stripping.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
