Roll out ecosystem code-style policy (swift-format + SwiftLint + comment-ratio nudge)

[gsdali]

What

Roll out the ecosystem's proposed code-style policy to this repo: swift-format +
SwiftLint (scoped to orphaned_doc_comment) as blocking CI, plus a non-blocking
comment:code ratio nudge script.

Proposal doc: ecosystem docs/code-style-policy-proposal-2026-08.md

Precedent: OCCTSwiftScripts#114 /
OCCTSwiftScripts#115, the reference
implementation for a repo this size.

Scope for this repo

This codebase is tiny (~547 Swift lines across 4 files: Sources/SwiftMeshHeal/MeshHeal.swift,
Sources/SwiftMeshHeal/HoleFill.swift, Tests/SwiftMeshHealTests/MeshHealTests.swift), so this
is a full sweep, not a gradual exemption-manifest rollout the way OCCTSwift needs at its
size:

• .swift-format (100 col, 4-space, copied verbatim from OCCTSwiftScripts' config) +
  a full swift-format --in-place --recursive sweep of Sources/ + Tests/.
• .swiftlint.yml, scoped to only_rules: [orphaned_doc_comment]: SwiftLint's default rule set
  duplicates swift-format's formatting opinions and separately opens a code-quality/complexity
  surface that overlaps the ecosystem's own code-structure policy rather than this one.
• Scripts/comment-ratio-check.sh: report-only nudge (never fails), bash to match this repo's
  own convention.
• .github/workflows/code-style.yml: swift-format lint --strict and swiftlint lint --strict
  as blocking gates, comment-ratio as a non-blocking step.
• okf/policies/code-style.md, linked from okf/index.md.
• Hand-fix every remaining swift-format lint --strict / swiftlint lint --strict finding that
  --in-place can't auto-fix (doc-comment structure, orphaned doc comments, etc.) until both
  tools report zero violations.

Explicitly out of scope here

• clang-format: zero first-party C++ bridge files in this repo (confirmed).
• Any docs-drift checks beyond what's already covered by this repo's existing
  docs-current/context-first policies: this repo's docs/reference/MeshHeal.md isn't the
  CLI-verb-table shape those checks target elsewhere in the ecosystem.

Process

Filed per the ecosystem policy's own gate: no repo implements without a filed issue first. PR to
follow, referencing this issue. Zero behavior change: swift build/swift test verified
before and after. Holding for review before merge.