P6: convert settler to platform infrastructure

Refactor of settler to use BaseNodeAdapter + commandRegistry + statusBadge.
settler follows the platform refactor plan in .claude/refactor/MODULE_SPLIT.md.
Tests stay green; CONTRACT.md generated; legacy aliases preserved.

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

test/basic/specificClass.basic.test.js

@@ -0,0 +1,123 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const EventEmitter = require('events');
+const Settler = require('../../src/specificClass');
+
+const NUM_SPECIES = 13;
+
+function makeSettler() {
+  return new Settler({
+    general: { name: 'TestSettler', id: 'settler-test-1', logging: { enabled: false, logLevel: 'error' } },
+    functionality: { softwareType: 'settler', positionVsParent: 'downstream' },
+  });
+}
+
+test('constructor sets default state', () => {
+  const s = makeSettler();
+  assert.equal(s.F_in, 0);
+  assert.deepEqual(s.Cs_in, new Array(NUM_SPECIES).fill(0));
+  assert.equal(s.C_TS, 2500);
+  assert.equal(s.upstreamReactor, null);
+  assert.equal(s.returnPump, null);
+});
+
+test('getEffluent conserves total flow (mass balance)', () => {
+  const s = makeSettler();
+  s.F_in = 200;
+  s.C_TS = 3000;
+  const C = new Array(NUM_SPECIES).fill(5);
+  C[12] = 2000;
+  s.Cs_in = C;
+  const [eff, sur, ret] = s.getEffluent;
+  assert.equal(eff.topic, 'Fluent');
+  assert.ok(Math.abs(eff.payload.F + sur.payload.F + ret.payload.F - 200) < 1e-6);
+  for (let i = 7; i <= 12; i++) assert.equal(eff.payload.C[i], 0);
+});
+
+test('getEffluent clamps F_s to F_in when X_TS exceeds C_TS', () => {
+  const s = makeSettler();
+  s.F_in = 100;
+  s.C_TS = 1000;
+  s.Cs_in = new Array(NUM_SPECIES).fill(10);
+  s.Cs_in[12] = 5000;
+  const [eff] = s.getEffluent;
+  assert.equal(eff.payload.F, 0);
+});
+
+test('reactor stateChange pulls effluent (preserves _connectReactor integration)', () => {
+  const s = makeSettler();
+  let outputChanges = 0;
+  s.emitter.on('output-changed', () => outputChanges++);
+
+  const reactor = {
+    config: { general: { name: 'r', id: 'r-1' }, functionality: { positionVsParent: 'upstream' } },
+    emitter: new EventEmitter(),
+    measurements: { emitter: new EventEmitter() },
+    // Mirror the array shape the reactor produces in production.
+    get getEffluent() {
+      const C = new Array(NUM_SPECIES).fill(2);
+      C[12] = 3500;
+      return [{ topic: 'Fluent', payload: { inlet: 0, F: 150, C } }];
+    },
+  };
+  s.router.dispatchRegister(reactor, 'reactor');
+  reactor.emitter.emit('stateChange');
+
+  assert.equal(s.upstreamReactor, reactor);
+  assert.equal(s.F_in, 150);
+  assert.equal(s.Cs_in[12], 3500);
+  assert.ok(outputChanges >= 1, 'reactor stateChange should trigger output-changed');
+});
+
+test('reactor stateChange handles single-envelope getEffluent (not array)', () => {
+  const s = makeSettler();
+  const reactor = {
+    config: { general: { name: 'r', id: 'r-1' }, functionality: { positionVsParent: 'upstream' } },
+    emitter: new EventEmitter(),
+    measurements: { emitter: new EventEmitter() },
+    get getEffluent() {
+      const C = new Array(NUM_SPECIES).fill(1);
+      C[12] = 800;
+      return { topic: 'Fluent', payload: { inlet: 0, F: 42, C } };
+    },
+  };
+  s.router.dispatchRegister(reactor, 'reactor');
+  reactor.emitter.emit('stateChange');
+
+  assert.equal(s.F_in, 42);
+  assert.equal(s.Cs_in[12], 800);
+});
+
+test('TSS measurement updates C_TS via _updateMeasurement', () => {
+  const s = makeSettler();
+  s._updateMeasurement('quantity (tss)', 7000);
+  assert.equal(s.C_TS, 7000);
+});
+
+test('downstream machine becomes returnPump', () => {
+  const s = makeSettler();
+  const pump = {
+    config: { general: { name: 'pump', id: 'p-1' }, functionality: { positionVsParent: 'downstream' } },
+    measurements: { emitter: new EventEmitter() },
+  };
+  s.router.dispatchRegister(pump, 'machine');
+  assert.equal(s.returnPump, pump);
+  assert.equal(pump.upstreamSource, s);
+});
+
+test('getStatusBadge returns idle when F_in=0, green when flowing', () => {
+  const s = makeSettler();
+  const idle = s.getStatusBadge();
+  assert.equal(idle.fill, 'blue');
+
+  s.F_in = 100;
+  s.C_TS = 5000;
+  const C = new Array(NUM_SPECIES).fill(10);
+  C[12] = 3000;
+  s.Cs_in = C;
+  const active = s.getStatusBadge();
+  assert.equal(active.fill, 'green');
+  assert.ok(active.text.includes('F_in'));
+});