fix: decode Git-quoted diff paths

[rogerchappel]

Summary

• decode Git C-style quoted paths, including control escapes, quotes, backslashes, and octal UTF-8 bytes
• apply decoding to modification and rename headers while preserving ordinary filenames with spaces
• cover real Git scan output for modified, renamed, added, deleted, and binary files
• document the compatibility fix in the changelog

Commits

• b861186 test: cover Git-quoted diff paths — unit and real-Git scan regressions
• 1af6fda fix: decode Git path quoting in unified diffs — parser implementation
• 00d5a96 test: preserve change metadata for unusual paths — add/delete/binary metadata coverage
• 91ab30d docs: note quoted path compatibility — changelog entry

Verification

• npm ci
• npm run release:check
• git diff --check origin/main...HEAD
• identity audit: all four commits authored and committed by Roger Chappel miscanalysis@gmail.com

Closes task #849.