Measure engine coupling and run the contract suite on the real engines

scripts/report-engine-coupling.mjs counts the engine-specific code left
outside src/globe/cesium and src/globe/navara: layer renderer lines per
engine, Cesium imports, `viewer` mentions, engine-name checks, raw Navara
reads, Navara ground passes, Cesium SDK loads and ScreenSpaceEventHandler
users. engineCoupling.test.mjs fails npm test when a count grows past
scripts/engine-coupling-baseline.json, so each step towards drawing
through the globe contract can only lower them.

scripts/qa-contract-suite.mjs runs src/globe/testing/contractSuite.mjs in
headless Chrome on the Cesium and Navara of a keyless dev server, which
until now only ran on the fake engine. The page imports the suite from the
dev server, starts at a fixed view, waits for the camera to rest and lets
the pointer through the panels. Cesium passes 57 of 57 checks, Navara 64
of 67; docs/CURRENT-STATE.md names the three that fail.

scripts/engineCoupling.test.mjs

@@ -0,0 +1,41 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import {
+  ENGINE_COUPLING_METRICS,
+  couplingGrowth,
+  measureEngineCoupling,
+  readBaseline,
+} from './report-engine-coupling.mjs';
+
+test('engine coupling does not grow past the baseline', () => {
+  const growth = couplingGrowth(
+    measureEngineCoupling(),
+    readBaseline().metrics,
+  );
+  assert.deepEqual(
+    growth,
+    [],
+    'Code outside the globe engines grew more engine-specific. Draw through ' +
+      'the globe contract instead; only a deliberate exception may raise ' +
+      'scripts/engine-coupling-baseline.json (--write-baseline).',
+  );
+});
+
+test('the baseline names every metric', () => {
+  const { metrics } = readBaseline();
+  assert.deepEqual(
+    Object.keys(metrics).sort(),
+    ENGINE_COUPLING_METRICS.map(({ id }) => id).sort(),
+  );
+});
+
+test('a metric that grows is reported, one that falls is not', () => {
+  const baseline = Object.fromEntries(
+    ENGINE_COUPLING_METRICS.map(({ id }) => [id, 10]),
+  );
+  const measured = { ...baseline, viewerLines: 11, navaraKindChecks: 3 };
+  assert.deepEqual(
+    couplingGrowth(measured, baseline).map(({ id }) => id),
+    ['viewerLines'],
+  );
+});