fix: production hardening — safety fixes, prediction accuracy, test coverage

Safety:
- Async input handler: await all handleInput() calls, prevents unhandled rejections
- Fix emergencyStop case mismatch: "emergencyStop" → "emergencystop" matching config
- Implement showCoG() method (was routing to undefined)
- Null guards on 6 methods for missing curve data
- Editor menu polling timeout (5s max)
- Listener cleanup on node close (child measurements + state emitter)
- Tick loop race condition: track startup timeout, clear on close

Prediction accuracy:
- Remove efficiency rounding that destroyed signal in canonical units
- Fix calcEfficiency variant: hydraulic power reads from correct variant
- Guard efficiency calculations against negative/zero values
- Division-by-zero protection in calcRelativeDistanceFromPeak
- Curve data anomaly detection (cross-pressure median-y ratio check)
- calcEfficiencyCurve O(n²) → O(n) with running min
- updateCurve bootstraps predictors when they were null

Tests: 43 new tests (76 total) covering emergency stop, shutdown/maintenance
sequences, efficiency/CoG, movement lifecycle, output format, null guards,
and listener cleanup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test/edge/negative-zero-guards.edge.test.js

@@ -0,0 +1,132 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const Machine = require('../../src/specificClass');
+const { makeMachineConfig, makeStateConfig } = require('../helpers/factories');
+
+test('calcEfficiency with zero power and flow does not produce efficiency value', () => {
+  const machine = new Machine(makeMachineConfig(), makeStateConfig({ state: { current: 'operational' } }));
+
+  machine.measurements.type('pressure').variant('measured').position('downstream').value(1000, Date.now(), 'mbar');
+  machine.measurements.type('pressure').variant('measured').position('upstream').value(800, Date.now(), 'mbar');
+  machine.measurements.type('flow').variant('predicted').position('atEquipment').value(0, Date.now(), 'm3/h');
+  machine.measurements.type('power').variant('predicted').position('atEquipment').value(0, Date.now(), 'kW');
+
+  // Should not throw
+  assert.doesNotThrow(() => machine.calcEfficiency(0, 0, 'predicted'));
+});
+
+test('calcEfficiency with negative power does not produce corrupt efficiency', () => {
+  const machine = new Machine(makeMachineConfig(), makeStateConfig({ state: { current: 'operational' } }));
+
+  machine.measurements.type('pressure').variant('measured').position('downstream').value(1000, Date.now(), 'mbar');
+  machine.measurements.type('pressure').variant('measured').position('upstream').value(800, Date.now(), 'mbar');
+  machine.measurements.type('flow').variant('predicted').position('atEquipment').value(100, Date.now(), 'm3/h');
+  machine.measurements.type('power').variant('predicted').position('atEquipment').value(-5, Date.now(), 'kW');
+
+  // Should not crash or produce negative efficiency
+  assert.doesNotThrow(() => machine.calcEfficiency(-5, 100, 'predicted'));
+
+  const eff = machine.measurements.type('efficiency').variant('predicted').position('atEquipment').getCurrentValue();
+  // Efficiency should not have been updated with negative power (guard: power > 0)
+  assert.ok(eff === undefined || eff === null || eff >= 0, 'Efficiency should not be negative');
+});
+
+test('calcCog returns safe defaults when no curve data available', () => {
+  const machine = new Machine(
+    makeMachineConfig({ asset: { model: null } }),
+    makeStateConfig()
+  );
+
+  const result = machine.calcCog();
+
+  assert.equal(result.cog, 0);
+  assert.equal(result.cogIndex, 0);
+  assert.equal(result.NCog, 0);
+  assert.equal(result.minEfficiency, 0);
+});
+
+test('getCurrentCurves returns empty arrays when no curve data available', () => {
+  const machine = new Machine(
+    makeMachineConfig({ asset: { model: null } }),
+    makeStateConfig()
+  );
+
+  const { powerCurve, flowCurve } = machine.getCurrentCurves();
+
+  assert.deepEqual(powerCurve, { x: [], y: [] });
+  assert.deepEqual(flowCurve, { x: [], y: [] });
+});
+
+test('getCompleteCurve returns null when no curve data available', () => {
+  const machine = new Machine(
+    makeMachineConfig({ asset: { model: null } }),
+    makeStateConfig()
+  );
+
+  const { powerCurve, flowCurve } = machine.getCompleteCurve();
+
+  assert.equal(powerCurve, null);
+  assert.equal(flowCurve, null);
+});
+
+test('calcFlow returns 0 when no curve data available', () => {
+  const machine = new Machine(
+    makeMachineConfig({ asset: { model: null } }),
+    makeStateConfig({ state: { current: 'operational' } })
+  );
+
+  const flow = machine.calcFlow(50);
+  assert.equal(flow, 0);
+});
+
+test('calcPower returns 0 when no curve data available', () => {
+  const machine = new Machine(
+    makeMachineConfig({ asset: { model: null } }),
+    makeStateConfig({ state: { current: 'operational' } })
+  );
+
+  const power = machine.calcPower(50);
+  assert.equal(power, 0);
+});
+
+test('inputFlowCalcPower returns 0 when no curve data available', () => {
+  const machine = new Machine(
+    makeMachineConfig({ asset: { model: null } }),
+    makeStateConfig({ state: { current: 'operational' } })
+  );
+
+  const power = machine.inputFlowCalcPower(100);
+  assert.equal(power, 0);
+});
+
+test('getMeasuredPressure returns 0 when no curve data available', () => {
+  const machine = new Machine(
+    makeMachineConfig({ asset: { model: null } }),
+    makeStateConfig()
+  );
+
+  const pressure = machine.getMeasuredPressure();
+  assert.equal(pressure, 0);
+});
+
+test('updateCurve bootstraps predictors when they were null', () => {
+  const machine = new Machine(
+    makeMachineConfig({ asset: { model: null } }),
+    makeStateConfig()
+  );
+
+  assert.equal(machine.hasCurve, false);
+  assert.equal(machine.predictFlow, null);
+
+  // Load a real curve into a machine that started without one
+  const { loadCurve } = require('generalFunctions');
+  const realCurve = loadCurve('hidrostal-H05K-S03R');
+
+  assert.doesNotThrow(() => machine.updateCurve(realCurve));
+
+  assert.equal(machine.hasCurve, true);
+  assert.ok(machine.predictFlow !== null);
+  assert.ok(machine.predictPower !== null);
+  assert.ok(machine.predictCtrl !== null);
+});