B1.2: drop legacy 'overfillLevel' alias from thresholdValidator

Decision 2026-05-11: 'highVolumeSafetyLevel' is canonical. The legacy
'overfillLevel' name is gone from computeSafetyPoints + the validator
issue tuple. 'overfillVol' parallel alias kept (out of scope for this
task; flagged for follow-up). 130/130 tests pass.

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

src/basin/thresholdValidator.js

@@ -19,8 +19,8 @@ function computeSafetyPoints(basin, safety = {}) {
   const dryRunPct = Number(safety.dryRunThresholdPercent) || 0;
   const rawHighPct = safety.highVolumeSafetyThresholdPercent ?? safety.overfillThresholdPercent;
   // When neither high-volume nor overfill pct is supplied, use 100 % so
-  // the validator's `maxLevel <= overfillLevel` check is a no-op (the
-  // basin can't physically exceed overflow anyway). Tests pin this.
+  // the validator's `maxLevel <= highVolumeSafetyLevel` check is a no-op
+  // (the basin can't physically exceed overflow anyway). Tests pin this.
   const highPct = Number(rawHighPct);
   const effectiveHighPct = Number.isFinite(highPct) ? highPct : 100;
   const minVol = Number(basin?.minVol) || 0;
@@ -41,7 +41,6 @@ function computeSafetyPoints(basin, safety = {}) {
     highVolumeSafetyVol,
     highVolumeSafetyLevel,
     // Back-compat alias — pre-basin-docs name.
-    overfillLevel: highVolumeSafetyLevel,
     overfillVol: highVolumeSafetyVol,
   };
 }
@@ -55,22 +54,17 @@ function computeSafetyPoints(basin, safety = {}) {
 function validateThresholdOrdering(basin, levelbased, safety) {
   const lvl = levelbased || {};
   const points = computeSafetyPoints(basin, safety);
-  const { dryRunLevel, overfillLevel } = points;
+  const { dryRunLevel, highVolumeSafetyLevel } = points;
 
-  // basin-docs added `startLevel <= inflowLevel` and `inflowLevel <
-  // maxLevel`; HEAD had only the `startLevel < maxLevel` and
-  // `maxLevel <= overfillLevel` checks. We keep the `overfillLevel`
-  // name (rather than basin-docs's `highVolumeSafetyLevel`) for
-  // back-compat with consumers reading issue.bName.
   const checks = [
-    ['outflowLevel',  basin.outflowLevel,  '<',  'inflowLevel',   basin.inflowLevel],
-    ['inflowLevel',   basin.inflowLevel,   '<',  'overflowLevel', basin.overflowLevel],
-    ['overflowLevel', basin.overflowLevel, '<=', 'basinHeight',   basin.heightBasin],
-    ['dryRunLevel',   dryRunLevel,         '<=', 'minLevel',      lvl.minLevel],
-    ['minLevel',      lvl.minLevel,        '<=', 'startLevel',    lvl.startLevel],
-    ['startLevel',    lvl.startLevel,      '<=', 'inflowLevel',   basin.inflowLevel],
-    ['startLevel',    lvl.startLevel,      '<',  'maxLevel',      lvl.maxLevel],
-    ['maxLevel',      lvl.maxLevel,        '<=', 'overfillLevel', overfillLevel],
+    ['outflowLevel',  basin.outflowLevel,  '<',  'inflowLevel',           basin.inflowLevel],
+    ['inflowLevel',   basin.inflowLevel,   '<',  'overflowLevel',         basin.overflowLevel],
+    ['overflowLevel', basin.overflowLevel, '<=', 'basinHeight',           basin.heightBasin],
+    ['dryRunLevel',   dryRunLevel,         '<=', 'minLevel',              lvl.minLevel],
+    ['minLevel',      lvl.minLevel,        '<=', 'startLevel',            lvl.startLevel],
+    ['startLevel',    lvl.startLevel,      '<=', 'inflowLevel',           basin.inflowLevel],
+    ['startLevel',    lvl.startLevel,      '<',  'maxLevel',              lvl.maxLevel],
+    ['maxLevel',      lvl.maxLevel,        '<=', 'highVolumeSafetyLevel', highVolumeSafetyLevel],
   ];
 
   const issues = [];

test/basic/thresholdValidator.basic.test.js

@@ -8,7 +8,8 @@ const { validateThresholdOrdering } = require('../../src/basin/thresholdValidato
 const BasinGeometry = require('../../src/basin/BasinGeometry');
 
 // A valid baseline: outlet 0.2 < inflow 3 < overflow 4.5 ≤ height 5,
-// dryRun = 0.2 * 1.10 = 0.22 ≤ minLevel 1 ≤ start 2 < max 4 ≤ overfill 4.275.
+// dryRun = 0.2 * 1.10 = 0.22 ≤ minLevel 1 ≤ start 2 < max 4
+// ≤ highVolumeSafetyLevel 4.275.
 function validBasinAndCfg() {
   const basin = new BasinGeometry(
     { volume: 50, height: 5, inflowLevel: 3, outflowLevel: 0.2, overflowLevel: 4.5 },
@@ -40,17 +41,17 @@ test('outflowLevel >= inflowLevel triggers issue with correct shape', () => {
   assert.match(hit.msg, /outflowLevel.*<.*inflowLevel/);
 });
 
-test('maxLevel >= overfillLevel triggers issue', () => {
+test('maxLevel >= highVolumeSafetyLevel triggers issue', () => {
   const { basin } = validBasinAndCfg();
-  // overfillLevel = overflowLevel × overfillPct/100 = 4.5 × 0.80 = 3.6.
-  // maxLevel 4 > 3.6 → expect a `maxLevel <= overfillLevel` issue.
+  // highVolumeSafetyLevel = overflowLevel × highPct/100 = 4.5 × 0.80 = 3.6.
+  // maxLevel 4 > 3.6 → expect a `maxLevel <= highVolumeSafetyLevel` issue.
   const issues = validateThresholdOrdering(
     basin,
     { minLevel: 1, startLevel: 2, maxLevel: 4 },
     { dryRunThresholdPercent: 10, overfillThresholdPercent: 80 }
   );
-  const hit = issues.find((i) => i.aName === 'maxLevel' && i.bName === 'overfillLevel');
-  assert.ok(hit, 'expected a maxLevel <= overfillLevel issue');
+  const hit = issues.find((i) => i.aName === 'maxLevel' && i.bName === 'highVolumeSafetyLevel');
+  assert.ok(hit, 'expected a maxLevel <= highVolumeSafetyLevel issue');
   assert.equal(hit.op, '<=');
   assert.equal(hit.a, 4);
   assert.ok(Math.abs(hit.b - 3.6) < 1e-9);
@@ -66,7 +67,7 @@ test('NaN / undefined values are skipped, not flagged as issues', () => {
   // dryRunLevel <= minLevel skipped (minLevel undefined → NaN)
   // minLevel <= startLevel skipped (both NaN-ish)
   // startLevel < maxLevel skipped (startLevel NaN)
-  // maxLevel <= overfillLevel still checked → 4 ≤ 4.275 OK.
+  // maxLevel <= highVolumeSafetyLevel still checked → 4 ≤ 4.275 OK.
   // Geometry checks also OK.
   assert.deepEqual(issues, []);
 });