Make public/rules-swift the canonical source (per project direction) and adopt
its opt-in lint rules that PureXML lacked: empty_count, explicit_init, first_where,
sorted_first_last, unused_import, plus its todo disable. All pass with zero
violations on the existing sources.
PureXML keeps its coherent, stricter tuning where the canon is a self-described
'starting point': force_unwrapping/force_try/force_cast = error (safety), and
trailing commas mandated in both swiftformat (--commas always) and swiftlint
(mandatory_comma) to resolve the canon's formatter-adds vs linter-flags mismatch.
docs/rules/README.md now points at public/rules-swift and documents the tuning.
Mihaela Mihaljevic
c6f305357c