Test layers on one engine and share selection and shader helpers

Layer display tests no longer re-check Cesium primitives in every layer:
they run on the fake engine, and one Cesium translation check per ground
kind lives in the Cesium engine's ground tests. Their harnesses are shared,
and the fake-engine, Cesium-engine and flights tests that repeated the
contract suite are gone, 340 tests in all.

The press-travel measurement is shared by the selection dispatcher and
CCTV, which loses its ScreenSpaceEventHandler shim and world-click module.
ALPR, installations and bikeshare share one selection keeper and selected
marker write. Layers with their own click rules keep their handlers.

Navara's pulse is a class like the ground pass, the ground and imagery
passes share the surface uniforms, and the colour, log-depth and occlusion
GLSL lives in one chunk module, each caller keeping its depth bias. The
ground suite runs inside the contract suite (--only=ground:), and fixture
and script names say what they test.

Behaviour is unchanged on both engines.

scripts/qa-l9-matrix.mjs

@@ -1086,15 +1086,25 @@ check({
   heavy: true, run: harness({ id: 'D1', script: 'track-regression.mjs', args: ['--url', APP_URL], timeoutMs: 1200000 }),
 });
 check({
-  id: 'D2', group: 'D', desc: 'qa-heading-b3 — path-derived display heading',
-  heavy: true, run: harness({ id: 'D2', script: 'qa-heading-b3.mjs', args: ['--url', APP_URL], timeoutMs: 900000 }),
+  id: 'D2',
+  group: 'D',
+  desc: 'qa-aircraft-heading — path-derived display heading',
+  heavy: true,
+  run: harness({
+    id: 'D2',
+    script: 'qa-aircraft-heading.mjs',
+    args: ['--url', APP_URL],
+    timeoutMs: 900000,
+  }),
 });
 check({
-  id: 'D3', group: 'D', desc: 'qa-sprites-b5 — per-class billboard silhouettes',
+  id: 'D3',
+  group: 'D',
+  desc: 'qa-aircraft-sprites — per-class billboard silhouettes',
   heavy: true,
   run: harness({
     id: 'D3',
-    script: 'qa-sprites-b5.mjs',
+    script: 'qa-aircraft-sprites.mjs',
     args: ['--url', APP_URL],
     timeoutMs: 900000,
     knownConditions: [{