Preserve stored unified-diff bytes through whitespace CI

Stored unified diffs are evidence data, and their blank context lines can contain a literal space that ordinary whitespace CI rejects. Trimming or reformatting the artifact changes its hash and may destroy replay semantics. Preserve its exact bytes, use a narrowly scoped Git attribute for those stored patch files, and keep normal source and documentation whitespace checks enabled. Test both sides with a patch fixture and an ordinary bad source line, then verify every published artifact hash against its receipt. Preserve line endings too when byte hashes matter. This exception is for evidence files, not newly implemented production code.

Applies when: A controlled coding or verification workflow uses this boundary. Keywords: Git unified diff patch evidence whitespace CI artifact hash