chore(#36): trial the ecosystem code-style policy

[gsdali]

What & why

Pilot repo for the ecosystem's proposed code-style policy
(ecosystem docs/code-style-policy-proposal-2026-08.md),
following the reference rollout at
OCCTSwiftScripts#114 /
#115. This repo is small (24 Swift
files, ~2,459 lines), so a full sweep rather than a gradual exemption manifest: bring the whole
tree into compliance in one PR and go straight to a blocking gate.

Adds:

• .swift-format (100 col, 4-space, the ecosystem's one deliberate divergence from Google's
  2-space default), copied verbatim from OCCTSwiftScripts, plus a full swift-format --in-place
  sweep of Sources/ + Tests/.
• .swiftlint.yml, scoped to only_rules: [orphaned_doc_comment], same rationale as the reference
  repo: SwiftLint's defaults duplicate swift-format's formatting opinions and open a separate
  code-quality/complexity surface that belongs to the ecosystem's own code-structure policy, not
  this one.
• Scripts/comment-ratio-check.sh: report-only nudge (never fails). This bootstraps the repo's
  first Scripts/ directory.
• .github/workflows/code-style.yml: swift-format lint --strict and swiftlint lint --strict
  as blocking gates, comment-ratio as a non-blocking step. This bootstraps the repo's first CI
  workflow; there was no GitHub Actions setup here before this PR.
• okf/policies/code-style.md, linked from okf/index.md, matching this repo's existing
  frontmatter conventions.
• 38 by-hand fixes for lint-only findings swift-format --in-place can't auto-fix:
  • BeginDocumentationCommentWithOneLineSummary (28 doc comments): split into a one-sentence
    summary, a blank /// line, then the detail, across Mesh.swift (x4), GLTFAdapter.swift,
    MeshIO.swift (x2), OBJ.swift, STL.swift, PLY.swift, ThreeMFAdapter.swift (x3),
    CADBodyMetadata.swift, DXFLoader.swift (x3), ShapeLoader.swift (x7), and four Tests
    files.
  • EndOfLineComment (4): trailing comments that pushed the line past the column limit,
    moved to their own line above (GLTFAdapter.swift, MeshIO.swift, DXFLoader.swift,
    DXFLoaderTests.swift).
  • AlwaysUseLowerCamelCase (4 declarations, local-only): export_ renamed to exported
    everywhere it appeared, one declaration in MLExport.swift and three separate local
    declarations across MLExportTests.swift's test functions, each updated in place.
  • Two "terminate this sentence with a period" fixes (DXFLoaderTests.swift,
    JWWLoaderTests.swift): a trailing parenthetical restructured so the doc comment's last
    character is a period, not a closing paren.

Also clears every em-dash from every file this sweep touches, per this repo's own
writing-style policy ("clear them from any file you are already
editing"). One deliberate exception: Sources/MeshIO/OBJ.swift's exported-file header comment
("# MeshIO OBJ ...") is left as-is, since it's a string literal written into the output file
(runtime content, not source-level prose), and changing it would be a behavior change outside this
PR's scope.

Explicitly out of scope here (matching the pilot repo's precedent): clang-format, this repo
carries zero first-party C++ bridge files, confirmed before starting.

Zero behavior change. All changes are formatting, doc-comment structure, or a local-only
rename; verified directly, not just asserted:

• swift-format lint --strict and swiftlint lint --strict: zero violations, both before commit.
• Scripts/comment-ratio-check.sh: runs clean (2 files flagged above the 1.0x nudge threshold,
  CADBodyMetadata.swift and ImportProgressClosure.swift; report-only, does not fail).
• swift build: succeeds identically before and after the sweep.
• OCCT_SERIAL=1 swift test --parallel --num-workers 1: 41/41 tests pass, same suite, same
  count, both before and after the sweep.
• No Package.resolved drift from any local build/test run.

Closes #36

Checklist

• New or changed behavior is covered by a unit test in the same PR (not just manual
  verification); see SecondMouseAU/OCCTReconstruct#397
  for the ecosystem-wide test-coverage standard this is piloting.
  N/A here: no behavior changed (formatting/doc-comments/CI only, one local-only rename),
  verified via the existing test suite (41/41 pass, identical before/after) rather than new
  tests, since there's no new behavior for a new test to cover.

Notes for the reviewer

Per the ecosystem's own gate (no repo implements without a filed issue first), this was filed as
#36 before any of this landed. Holding for review before merge, per the same process
OCCTSwiftScripts#115 followed.

Separately: this repo's okf/index.md currently links 4 of the ecosystem's 6 current mandatory
policies (missing issue-tracking and code-structure). Not addressed in this PR, out of scope
for a code-style rollout; flagging in case it is worth its own issue.

🤖 Generated with Claude Code