[key-r-code]

Summary

• adds the texdelta CLI, strict configuration, versioned reports, safe staging, BibTeX/latexpand/latexdiff orchestration, and accessible image comparisons
• adds deterministic synthetic fixtures, 90%+ coverage gates, Linux/macOS TeX builds, PDF checks, and a visual snapshot
• adds the bundled Overleaf zipapp and public documentation/governance files

Verification

• 41 tests pass locally with 92.34% branch-aware coverage
• Ruff and strict mypy pass
• wheel install, packaged init-overleaf, zipapp, and repeated latexmk smoke tests pass
• private regression passes: Figures 1–3 changed; Figures 5, 6, and 9 added; no removals; Figures 4, 7, and 8 recognized as renamed byte-identical assets and omitted from the appendix
• publication-safety scan found no manuscript content, private figures, datasets, credentials, personal email, or real home paths

This PR intentionally does not publish to PyPI, tag a release, or include private regression artifacts.