fix(diff): strip trailing CR from CRLF diff text (#1302)

ParseDiffText and ParseHunks split on "\n" and kept the carriage return that
CRLF-terminated diff text leaves on every line. It rode into the "diff --git"
capture, so NewPath became "file.go\r" and the file could not be read for
review, and it defeated the equality checks against "--- /dev/null", costing
a diff its IsNew or IsDeleted flag.

Fixes #933

Co-authored-by: SurefireStudios <heresamemo@gmail.com>
Co-authored-by: MeiSiristhebest <124799179+MeiSiristhebest@users.noreply.github.com>