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

.github/workflows/code-style.yml

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+name: code-style
+
+# Trial of the ecosystem's code-style policy (OCCTSwiftIO#36, following the
+# reference rollout at OCCTSwiftScripts#114/#115); see
+# docs/code-style-policy-proposal-2026-08.md in the `ecosystem` repo for the
+# full rationale. Full sweep rather than a gradual exemption manifest because
+# this repo is small enough to bring fully into compliance in one PR and go
+# straight to a blocking gate.
+#
+# Pure text analysis (formatting + lint), no compiled output needed by any of
+# the three checks, so this stays a macOS runner only because that's where
+# swift-format and swiftlint are both readily available via Homebrew.
+#
+# swift-format and SwiftLint are blocking: formatting has no judgment call in
+# it. The comment-ratio check is report-only by design (see the script's own
+# header) and is not a gate; it always exits 0.
+
+on:
+  push:
+    paths:
+      - 'Sources/**'
+      - 'Tests/**'
+      - '.swift-format'
+      - '.swiftlint.yml'
+      - 'Scripts/comment-ratio-check.sh'
+      - '.github/workflows/code-style.yml'
+  pull_request:
+    paths:
+      - 'Sources/**'
+      - 'Tests/**'
+      - '.swift-format'
+      - '.swiftlint.yml'
+      - 'Scripts/comment-ratio-check.sh'
+      - '.github/workflows/code-style.yml'
+  workflow_dispatch:
+
+jobs:
+  code-style:
+    runs-on: macos-15
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install swift-format and SwiftLint
+        run: brew install swift-format swiftlint
+
+      - name: swift-format lint --strict
+        run: |
+          find Sources Tests -name '*.swift' -print0 \
+            | xargs -0 swift-format lint --strict --configuration .swift-format
+
+      - name: swiftlint lint --strict
+        run: swiftlint lint --strict --config .swiftlint.yml
+
+      - name: Comment:code ratio (report-only, never fails)
+        run: Scripts/comment-ratio-check.sh

.swift-format

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+{
+  "version" : 1,
+  "lineLength" : 100,
+  "indentation" : {
+    "spaces" : 4
+  },
+  "tabWidth" : 4,
+  "maximumBlankLines" : 1,
+  "respectsExistingLineBreaks" : true,
+  "lineBreakBeforeControlFlowKeywords" : false,
+  "lineBreakBeforeEachArgument" : false,
+  "lineBreakBeforeEachGenericRequirement" : false,
+  "lineBreakBetweenDeclarationAttributes" : false,
+  "multiElementCollectionTrailingCommas" : true,
+  "prioritizeKeepingFunctionOutputTogether" : false,
+  "reflowMultilineStringLiterals" : "never",
+  "spacesAroundRangeFormationOperators" : false,
+  "spacesBeforeEndOfLineComments" : 2,
+  "fileScopedDeclarationPrivacy" : {
+    "accessLevel" : "private"
+  },
+  "orderedImports" : {
+    "includeConditionalImports" : false
+  },
+  "noAssignmentInExpressions" : {
+    "allowedFunctions" : [
+      "XCTAssertNoThrow"
+    ]
+  },
+  "rules" : {
+    "AllPublicDeclarationsHaveDocumentation" : false,
+    "AlwaysUseLiteralForEmptyCollectionInit" : false,
+    "AlwaysUseLowerCamelCase" : true,
+    "AmbiguousTrailingClosureOverload" : true,
+    "AvoidRetroactiveConformances" : true,
+    "BeginDocumentationCommentWithOneLineSummary" : true,
+    "DoNotUseSemicolons" : true,
+    "DontRepeatTypeInStaticProperties" : true,
+    "FileScopedDeclarationPrivacy" : true,
+    "FullyIndirectEnum" : true,
+    "GroupNumericLiterals" : true,
+    "IdentifiersMustBeASCII" : true,
+    "NeverForceUnwrap" : false,
+    "NeverUseForceTry" : false,
+    "NeverUseImplicitlyUnwrappedOptionals" : false,
+    "NoAccessLevelOnExtensionDeclaration" : true,
+    "NoAssignmentInExpressions" : true,
+    "NoBlockComments" : true,
+    "NoCasesWithOnlyFallthrough" : true,
+    "NoEmptyLinesOpeningClosingBraces" : false,
+    "NoEmptyTrailingClosureParentheses" : true,
+    "NoLabelsInCasePatterns" : true,
+    "NoLeadingUnderscores" : false,
+    "NoParensAroundConditions" : true,
+    "NoPlaygroundLiterals" : true,
+    "NoVoidReturnOnFunctionSignature" : true,
+    "OmitExplicitReturns" : false,
+    "OneCasePerLine" : true,
+    "OneVariableDeclarationPerLine" : true,
+    "OnlyOneTrailingClosureArgument" : true,
+    "OrderedImports" : true,
+    "ReplaceForEachWithForLoop" : true,
+    "ReturnVoidInsteadOfEmptyTuple" : true,
+    "TypeNamesShouldBeCapitalized" : true,
+    "UseEarlyExits" : false,
+    "UseExplicitNilCheckInConditions" : true,
+    "UseLetInEveryBoundCaseVariable" : true,
+    "UseShorthandTypeNames" : true,
+    "UseSingleLinePropertyGetter" : true,
+    "UseSynthesizedInitializer" : true,
+    "UseTripleSlashForDocumentationComments" : true,
+    "UseWhereClausesInForLoops" : false,
+    "ValidateDocumentationComments" : true
+  }
+}

.swiftlint.yml

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+# Deliberately narrow: `only_rules`, not `disabled_rules`. SwiftLint's default
+# rule set covers two kinds of territory this repo doesn't want it opining on:
+#
+#   - Layout (colon/comma/opening_brace/line_length/...): swift-format already
+#     owns this; running both fights, since they can disagree on the same line.
+#   - Code-quality/complexity (identifier_name, cyclomatic_complexity,
+#     function_body_length, nesting, type_body_length, file_length, ...): a
+#     separate concern from code style, and one that overlaps the ecosystem's
+#     own code-structure policy (a repo that needs a structural pass runs one
+#     as its own scoped initiative, not as a side effect of a style-lint gate).
+#     identifier_name's default 3-char minimum in particular is not a fit for
+#     this codebase's short, conventional locals in dense numerical/graph code
+#     (i, db, g, sv, ev): 548 hits on first run in OCCTSwiftScripts, the sibling
+#     repo this config is ported from; none of them real problems.
+#
+# What's left is the one rule that catches something swift-format has no
+# equivalent for: a doc comment not attached to any declaration.
+#
+# See docs/code-style-policy-proposal-2026-08.md in the ecosystem repo for
+# the full rationale.
+
+only_rules:
+  - orphaned_doc_comment
+
+excluded:
+  - .build
+  - Tests

Scripts/comment-ratio-check.sh

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+#!/usr/bin/env bash
+# comment-ratio-check.sh: flag Swift files where comment lines outnumber code
+# lines, as a signal for a human to look, not a fail.
+#
+# Part of the ecosystem's code-style policy trial (OCCTSwiftIO#36, following
+# the reference rollout at OCCTSwiftScripts#114); see
+# docs/code-style-policy-proposal-2026-08.md in the `ecosystem` repo for the
+# full rationale. A high ratio is sometimes legitimate (a small function with
+# several real caveats worth spelling out) and sometimes means a doc comment
+# has drifted into restating design rationale that belongs in docs/ instead
+# (see the proposal's own CurveAdaptors.md finding for what that looks like
+# once it's had years to drift): this script surfaces the number, it doesn't
+# judge which case it is. Report-only: always exits 0, same as
+# check-docs-existence.py's own `--coverage` mode in OCCTSwift/Scripts, and
+# for the same reason: failing every file above a threshold on day one, in a
+# codebase nobody has swept yet, punishes the report instead of the problem.
+#
+# Usage:
+#   Scripts/comment-ratio-check.sh              # default threshold: 1.0
+#   Scripts/comment-ratio-check.sh 1.5           # custom threshold
+set -euo pipefail
+
+threshold="${1:-1.0}"
+
+[ -d Sources ] || { echo "FAIL: Sources/ not found; run from the repo root" >&2; exit 1; }
+
+flagged=0
+
+while IFS= read -r -d '' file; do
+    comment=0
+    code=0
+    while IFS= read -r line; do
+        trimmed="${line#"${line%%[![:space:]]*}"}"
+        [ -z "$trimmed" ] && continue
+        case "$trimmed" in
+            //*) comment=$((comment + 1)) ;;
+            *) code=$((code + 1)) ;;
+        esac
+    done < "$file"
+
+    [ "$code" -eq 0 ] && continue
+
+    # POSIX sh has no float math; compare as comment*100 >= threshold*code so
+    # a fractional threshold (the common case: 1.0, 1.5) still works exactly.
+    threshold_x100=$(awk -v t="$threshold" 'BEGIN { printf "%d", t * 100 }')
+    if [ $((comment * 100)) -ge $((threshold_x100 * code)) ]; then
+        ratio=$(awk -v c="$comment" -v d="$code" 'BEGIN { printf "%.2f", c / d }')
+        printf '  %-55s comment=%-5d code=%-5d ratio=%s\n' "$file" "$comment" "$code" "$ratio"
+        flagged=$((flagged + 1))
+    fi
+done < <(find Sources -name '*.swift' -print0 | sort -z)
+
+if [ "$flagged" -eq 0 ]; then
+    echo "comment-ratio-check: no files at or above ${threshold}x comment:code (Sources/)"
+else
+    echo "comment-ratio-check: $flagged file(s) at or above ${threshold}x comment:code (Sources/), not a failure, a signal to look"
+fi
+
+exit 0