feat(iace): OSHA minimum-distance library — Task #18

Verbatim OSHA 29 CFR 1910 Subpart O values anchored as the rechtssicher
zitierbare Werte-Basis for the IACE engine. Per strategy discussion
(2026-05-20) US Federal Code is the only public-domain corpus we can
reproduce wholesale; DIN/EN values stay identifier-only.

Coverage in this initial batch:
- MD_OSHA_O10_R1, MD_OSHA_O10_R4 (Table O-10 rows 1 + 4 — point of
  operation guard distance vs max opening width)
- MD_OSHA_212_FAN (§1910.212(a)(5) fan-blade guards: 1/2 in)
- MD_OSHA_217_PSDI (§1910.217 hand-speed constant 63 in/s for
  presence-sensing-device-initiation and two-hand-trip distances)

Each entry carries four parallel value sets:
- OriginalValue/Min/Max in source unit (verbatim, R1)
- ExactMM via deterministic conversion (mathematics, no copyright)
- RecommendedMM with safe-side rounding documented in RoundingNote
- EUNormHints — identifier-only references to EN ISO 13857, EN 13855,
  EN 349 with a human-curated DINComparisonNote (qualitative judgement,
  not a copy)

Open follow-ups (separate iterations):
- Full Table O-10 (rows 2-10) — same shape
- §1910.219 mechanical power-transmission distances
- Cross-reference IACE patterns to MD_OSHA_* identifiers so the Suppression
  Engine surfaces concrete metric values in mitigation suggestions
- Frontend integration: <MinimumDistanceCard> for each measure

ai-compliance-sdk/internal/iace/minimum_distances.go

@@ -0,0 +1,172 @@
+package iace
+
+// Minimum-distance library — Task #18.
+//
+// Anchor source: OSHA 29 CFR 1910 Subpart O (US Federal Public Domain,
+// 17 U.S.C. §105). The values below are reproduced verbatim from the
+// Federal Code; conversions to metric are mathematical and carry no
+// copyright. Engineering rounding to safe-side mm values is BreakPilot's
+// recommendation and labelled as such.
+//
+// EU norm equivalents (EN ISO 13857, EN 349, EN 13855, EN 1010) are
+// referenced by identifier only — no values are reproduced, because
+// DIN/Beuth retain copyright on the wording. The DINComparisonNote
+// field carries a human-curated judgement on whether the EU norm is
+// stricter / looser / equivalent — this is a qualitative observation
+// about a publicly available document, not a copy of its text.
+//
+// See LICENSE_RULES.md and project_attribution_strategy.md for the
+// licensing logic. The OSHA values are R1 (verbatim public domain);
+// the recommended metric values are BreakPilot engineering output (R3
+// own-work). DIN references are R3 identifier-only.
+
+// MinimumDistanceUnit denotes the original unit system of the source.
+type MinimumDistanceUnit string
+
+const (
+	UnitInch   MinimumDistanceUnit = "inch"
+	UnitFoot   MinimumDistanceUnit = "foot"
+	UnitMeter  MinimumDistanceUnit = "meter"
+	UnitMM     MinimumDistanceUnit = "mm"
+)
+
+// MinimumDistance is the data contract for a single safety-distance rule.
+// It can be (a) a fixed gap value, (b) a distance range, or (c) a formula
+// like OSHA's Ds = 63 in/s × Ts (hand-speed constant).
+type MinimumDistance struct {
+	ID string `json:"id"` // MD_OSHA_001
+	// Source identifier — full CFR citation or norm reference.
+	SourceCFR    string `json:"source_cfr,omitempty"`    // "29 CFR §1910.217(c)(1)(i)"
+	SourceTable  string `json:"source_table,omitempty"`  // "Table O-10"
+	License      string `json:"license"`                 // "US Federal Public Domain"
+	LicenseRule  int    `json:"license_rule"`            // 1 / 2 / 3 (see LICENSE_RULES.md)
+
+	// Original verbatim value in the source's own unit.
+	OriginalUnit    MinimumDistanceUnit `json:"original_unit"`
+	OriginalValue   float64             `json:"original_value,omitempty"`
+	OriginalMin     float64             `json:"original_min,omitempty"`
+	OriginalMax     float64             `json:"original_max,omitempty"`
+
+	// Exact conversion to mm — no engineering rounding.
+	ExactMM    float64 `json:"exact_mm,omitempty"`
+	ExactMinMM float64 `json:"exact_min_mm,omitempty"`
+	ExactMaxMM float64 `json:"exact_max_mm,omitempty"`
+
+	// Engineering-recommended metric value with safe-side rounding.
+	// For minimum distances: rounded up. For maximum opening widths:
+	// rounded down.
+	RecommendedMM    int `json:"recommended_mm,omitempty"`
+	RecommendedMinMM int `json:"recommended_min_mm,omitempty"`
+	RecommendedMaxMM int `json:"recommended_max_mm,omitempty"`
+	RoundingNote string `json:"rounding_note,omitempty"`
+
+	// Optional formula constant (e.g. OSHA hand-speed 63 in/s).
+	FormulaInchPerSecond float64 `json:"formula_inch_per_second,omitempty"`
+	FormulaMMPerSecond   float64 `json:"formula_mm_per_second,omitempty"`
+	FormulaDescription   string  `json:"formula_description,omitempty"`
+
+	Context  string   `json:"context"`              // "Point of Operation Guarding mechanical presses"
+	BodyPart string   `json:"body_part,omitempty"`  // "finger" / "hand" / "head" / "foot" / "body"
+	HazardTags []string `json:"hazard_tags,omitempty"` // [crush_point, cutting_part, ...]
+
+	// EU norm cross-reference — IDENTIFIER ONLY, no values reproduced.
+	EUNormHints []EUNormHint `json:"eu_norm_hints,omitempty"`
+}
+
+// EUNormHint references an EU standard by identifier without reproducing
+// any value or text from it. The DINComparisonNote is a human-curated
+// qualitative judgement (stricter / equivalent / looser) — not a copy.
+type EUNormHint struct {
+	Norm            string `json:"norm"`             // "EN ISO 13857"
+	Section         string `json:"section,omitempty"` // "Tab. 4, Schutz gegen Hineingreifen"
+	DINComparisonNote string `json:"din_comparison_note,omitempty"`
+}
+
+// GetOSHAMinimumDistances returns the verbatim OSHA values for
+// machine-guarding distances. All values are US Federal Public Domain
+// (17 U.S.C. §105). Engineering rounding is BreakPilot's safe-side
+// recommendation; OSHA values themselves are unchanged.
+func GetOSHAMinimumDistances() []MinimumDistance {
+	return []MinimumDistance{
+		// OSHA Table O-10 row 1 — verbatim values, mathematical conversion,
+		// safe-side rounded engineering recommendation.
+		{
+			ID:           "MD_OSHA_O10_R1",
+			SourceCFR:    "29 CFR §1910.217(c)(1)(i)",
+			SourceTable:  "Table O-10 row 1",
+			License:      "US Federal Public Domain (17 U.S.C. §105)",
+			LicenseRule:  1,
+			OriginalUnit: UnitInch,
+			OriginalMin:  0.5, OriginalMax: 1.5, OriginalValue: 0.25,
+			ExactMinMM:   12.7, ExactMaxMM: 38.1, ExactMM: 6.35,
+			RecommendedMinMM: 15, RecommendedMaxMM: 40, RecommendedMM: 6,
+			RoundingNote:     "Distance auf 5-mm-Raster aufgerundet, opening auf 1-mm-Raster abgerundet (konservativ in beide Richtungen).",
+			Context:          "Point-of-Operation Guarding bei mechanischen Pressen",
+			BodyPart:         "finger",
+			HazardTags:       []string{"crush_point", "cutting_part"},
+			EUNormHints: []EUNormHint{
+				{Norm: "EN ISO 13857", Section: "Tab. 4 (Hineingreifen)",
+					DINComparisonNote: "Andere Methodik (Reichweitenmodell). Unabhaengig pruefen — Werte koennen abweichen."},
+			},
+		},
+		// OSHA Table O-10 row 4 — used as a worked example in the strategy
+		// discussion. Distance 3.5-5.5 in, opening max 5/8 in.
+		{
+			ID:           "MD_OSHA_O10_R4",
+			SourceCFR:    "29 CFR §1910.217(c)(1)(i)",
+			SourceTable:  "Table O-10 row 4",
+			License:      "US Federal Public Domain (17 U.S.C. §105)",
+			LicenseRule:  1,
+			OriginalUnit: UnitInch,
+			OriginalMin:  3.5, OriginalMax: 5.5, OriginalValue: 0.625,
+			ExactMinMM:   88.9, ExactMaxMM: 139.7, ExactMM: 15.875,
+			RecommendedMinMM: 90, RecommendedMaxMM: 140, RecommendedMM: 15,
+			RoundingNote:     "Distance 88.9→90 (+1.1 mm), 139.7→140 (+0.3 mm) aufgerundet; Opening 15.875→15 (-0.875 mm) abgerundet.",
+			Context:          "Point-of-Operation Guarding bei mechanischen Pressen",
+			BodyPart:         "finger",
+			HazardTags:       []string{"crush_point", "cutting_part"},
+			EUNormHints: []EUNormHint{
+				{Norm: "EN ISO 13857", Section: "Tab. 4 (Hineingreifen)",
+					DINComparisonNote: "Andere Methodik (Reichweitenmodell). Compliance-Annotation pflegen."},
+			},
+		},
+		// OSHA §1910.212(a)(5) — fan blade guards. Verbatim 1/2 inch.
+		{
+			ID:           "MD_OSHA_212_FAN",
+			SourceCFR:    "29 CFR §1910.212(a)(5)",
+			License:      "US Federal Public Domain (17 U.S.C. §105)",
+			LicenseRule:  1,
+			OriginalUnit: UnitInch,
+			OriginalValue: 0.5,
+			ExactMM:      12.7,
+			RecommendedMM: 12,
+			RoundingNote: "Luefterblatt-Schutzgitter: max. Spaltoeffnung 1/2 in = 12.7 mm. Konservativ auf 12 mm abgerundet.",
+			Context:      "Lüfterblätter unter 7 ft (2.13 m) Höhe",
+			BodyPart:     "finger",
+			HazardTags:   []string{"rotating_part", "cutting_part"},
+			EUNormHints: []EUNormHint{
+				{Norm: "EN ISO 13857", Section: "Tab. 4",
+					DINComparisonNote: "DIN-Wert pruefen."},
+			},
+		},
+		// OSHA §1910.217 Hand-Speed Constant — formula Ds = 63 in/s × Ts
+		{
+			ID:           "MD_OSHA_217_PSDI",
+			SourceCFR:    "29 CFR §1910.217 (Ds = 63 in/s × Ts)",
+			License:      "US Federal Public Domain (17 U.S.C. §105)",
+			LicenseRule:  1,
+			OriginalUnit: UnitInch,
+			FormulaInchPerSecond: 63.0,
+			FormulaMMPerSecond:   1600.2,
+			FormulaDescription: "Hand-Speed-Konstante 63 in/s ≈ 1600 mm/s. " +
+				"Ds (Mindestabstand) = 63 × Ts (Stoppzeit Presse in Sekunden).",
+			Context:    "PSDI Presence-Sensing Device Initiation und Two-Hand-Trip",
+			BodyPart:   "hand",
+			HazardTags: []string{"crush_point", "high_speed"},
+			EUNormHints: []EUNormHint{
+				{Norm: "EN 13855", Section: "Sicherheitsabstaende",
+					DINComparisonNote: "EN 13855 nutzt andere Konstante (1600 mm/s ≈ identisch); EU-Norm unabhaengig pruefen."},
+			},
+		},
+	}
+}