Adopt the rules-swift pin-and-codify strategy in snapshot mode (third_party/rules-swift
@97dc70f + sha256), add codified gates, a conformance audit ledger, and
.github/workflows/rules-swift.yml (corpus-pin integrity required, full gate report mode).
Remove the docs/rules mirror it supersedes (repo-specific files kept under docs/). Style
and leak gates exclude the vendored corpus.
Follow the mihaela-agents mermaid rule: add a README roadmap using the TileDown
Apple-color status classes (done/review/epic/todo), legend block first, then a
libxml2-parity roadmap showing shipped vs open work. Add docs/rules/mermaid.md
and scripts/check-roadmap.sh (wired into check-all.sh) so the diagrams stay
mechanically checkable.
