The attribution check spawned `git ls-files` but never looked at its
exit status: outside a usable checkout, or on a git error, the empty
output read as "no files" and the check passed with nothing checked.
A non-zero status is now an error with git's message.
The list is read NUL-separated (`-z`): without it git quotes a name
with non-ASCII letters ("assets/\303\251.png"), which matched no file
on disk and was silently left out of the check.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Clean-room foundations for WordCraft: Arc-shared document model with
paragraph/run editing, styles, lists, sections and tables; Word-style
font substitution; first-fit line breaking with tabs, lists, alignment,
pagination, tables, headers/footers and hit testing; vello_cpu page
rasteriser.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
