v0.28.0

What's Changed

• ci: bump pinned mdsmith baseline to v0.27.0 by @jeduden in #430
• Plan 215: mdsmith public engine API and WASM bindings by @jeduden in #423
• docs(install): document Homebrew + asdf channels; trigger tap bump on release by @jeduden in #434
• Plan 209: Convention-per-file config under .mdsmith/conventions/ by @jeduden in #431
• docs(vscode): redesign extension guide as a feature showcase by @jeduden in #436
• perf: eliminate hot-path allocations in five rules by @jeduden in #433
• perf: replace map[string]bool sets with map[string]struct{} and fix include double-conversion by @jeduden in #441
• Plan 220: Harden the git-index writers against a transient index.lock by @jeduden in #440

Full Changelog: v0.27.0...v0.28.0