refactor(units): route all conversions through UnitPolicy.convert

Delete the legacy _convertUnitValue helper on the domain and the
duplicate convertUnitValue export on curveNormalizer; both were
identical to UnitPolicy.convert. Callers in flowController, the
curve normalizer, and buildQHCurve now go through this.unitPolicy.
The contract in .claude/refactor/CONTRACTS.md §6 named these as the
target migration; this finishes the rollout for rotatingMachine.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/curves/curveNormalizer.js

@@ -1,39 +1,24 @@
-const { convert } = require('generalFunctions');
-
-/**
- * Strict numeric unit conversion. Mirrors specificClass._convertUnitValue
- * so the curve normalizer is testable without a Machine instance.
- */
-function convertUnitValue(value, fromUnit, toUnit, contextLabel = 'unit conversion') {
-  const numeric = Number(value);
-  if (!Number.isFinite(numeric)) {
-    throw new Error(`${contextLabel}: value '${value}' is not finite`);
-  }
-  if (!fromUnit || !toUnit || fromUnit === toUnit) return numeric;
-  return convert(numeric).from(fromUnit).to(toUnit);
-}
-
 /**
  * Convert one curve section (nq or np) from supplied units to canonical
- * units. Logs a warning when the per-pressure median y jumps by more than
- * 3x relative to the previous pressure level — that almost always means the
- * curve file is corrupt (mixed units, swapped rows) and the predict module
- * would otherwise silently produce nonsense values.
+ * units using the host UnitPolicy. Logs a warning when the per-pressure
+ * median y jumps by more than 3x relative to the previous pressure level —
+ * that almost always means the curve file is corrupt (mixed units, swapped
+ * rows) and the predict module would otherwise silently produce nonsense.
  */
-function normalizeCurveSection(section, fromYUnit, toYUnit, fromPressureUnit, toPressureUnit, sectionName, logger) {
+function normalizeCurveSection(section, unitPolicy, fromYUnit, toYUnit, fromPressureUnit, toPressureUnit, sectionName, logger) {
   const normalized = {};
   let prevMedianY = null;
 
   for (const [pressureKey, pair] of Object.entries(section || {})) {
-    const canonicalPressure = convertUnitValue(
+    const canonicalPressure = unitPolicy.convert(
       Number(pressureKey),
       fromPressureUnit,
       toPressureUnit,
-      `${sectionName} pressure axis`
+      `${sectionName} pressure axis`,
     );
     const xArray = Array.isArray(pair?.x) ? pair.x.map(Number) : [];
     const yArray = Array.isArray(pair?.y)
-      ? pair.y.map((v) => convertUnitValue(v, fromYUnit, toYUnit, `${sectionName} output`))
+      ? pair.y.map((v) => unitPolicy.convert(v, fromYUnit, toYUnit, `${sectionName} output`))
       : [];
     if (!xArray.length || !yArray.length || xArray.length !== yArray.length) {
       throw new Error(`Invalid ${sectionName} section at pressure '${pressureKey}'.`);
@@ -74,21 +59,23 @@ function normalizeMachineCurve(rawCurve, unitPolicy, logger) {
   return {
     nq: normalizeCurveSection(
       rawCurve.nq,
+      unitPolicy,
       curveUnits.flow,
       canonicalFlow,
       curveUnits.pressure,
       canonicalPressure,
       'nq',
-      logger
+      logger,
     ),
     np: normalizeCurveSection(
       rawCurve.np,
+      unitPolicy,
       curveUnits.power,
       canonicalPower,
       curveUnits.pressure,
       canonicalPressure,
       'np',
-      logger
+      logger,
     ),
   };
 }
@@ -114,4 +101,4 @@ function readCanonical(unitPolicy, type) {
   return (unitPolicy.canonical || {})[type] || null;
 }
 
-module.exports = { normalizeMachineCurve, normalizeCurveSection, convertUnitValue };
+module.exports = { normalizeMachineCurve, normalizeCurveSection };

src/display/workingCurves.js

@@ -79,6 +79,12 @@ function buildQHCurve(predictors, ctrlPct, options = {}) {
   if (!pf.inputCurve || typeof pf.inputCurve !== 'object') {
     return { error: NO_CURVE_ERROR, points: [] };
   }
+  const policy = options.unitPolicy || predictors.unitPolicy;
+  if (!policy) {
+    return { error: 'No unitPolicy available for Q-axis conversion', points: [] };
+  }
+  const flowFrom = policy.canonical?.flow || policy.canonical?.('flow');
+  const flowTo = policy.output?.flow || policy.output?.('flow');
   const x = Number.isFinite(+ctrlPct) ? +ctrlPct : (pf.currentX ?? 0);
   const RHO = 999.1;   // kg/m³ — water at ~15 °C
   const G = 9.80665;   // m/s²
@@ -103,7 +109,8 @@ function buildQHCurve(predictors, ctrlPct, options = {}) {
     for (const p of pressures) {
       pf.fDimension = p;
       const QM3s = pf.y(x);
-      points.push({ Q: QM3s * 3600, H: p / (RHO * G), dpPa: p });
+      const Q = policy.convert(QM3s, flowFrom, flowTo, 'buildQHCurve Q-axis');
+      points.push({ Q, H: p / (RHO * G), dpPa: p });
     }
   } finally {
     pf.fDimension = originalF;

src/flow/flowController.js

@@ -50,7 +50,7 @@ class FlowController {
           return await host.executeSequence(parameter);
 
         case 'flowmovement': {
-          const canonicalFlowSetpoint = host._convertUnitValue(
+          const canonicalFlowSetpoint = host.unitPolicy.convert(
             parameter,
             host.unitPolicy.output.flow,
             host.unitPolicy.canonical.flow,

src/specificClass.js

@@ -247,12 +247,6 @@ class Machine extends BaseDomain {
     if (!this.isUnitValidForType(type, u)) throw new Error(`Unsupported unit '${u}' for ${type} measurement.`);
     return u;
   }
-  _convertUnitValue(value, from, to, ctx = 'unit conversion') {
-    const n = Number(value);
-    if (!Number.isFinite(n)) throw new Error(`${ctx}: value '${value}' is not finite`);
-    if (!from || !to || from === to) return n;
-    return convert(n).from(from).to(to);
-  }
   _measurementPositionForMetric(metricId) { return metricId === 'power' ? 'atEquipment' : 'downstream'; }
   _resolveProcessRangeForMetric(metricId, predicted, measured) {
     let processMin = NaN; let processMax = NaN;