Delete dead render code and consolidate QA helpers

Remove code that nothing in the app, the runners or CI uses:
- the one-off migration compare, look and bench scripts and the vector
  ground prototype they measured, with the bench tables in the docs;
- the unused Navara-named shared render modules (polygons, ground picks,
  mover bank, ground ring);
- the Cesium-shaped aircraft and vessel test renderers, and the trail,
  engineFromViewer and horizon-occluder helpers only they kept alive.
  Their tests now run on the production displays over the fake engine;
- Navara's unread diagnostics, fallback ports, dead exports and
  parameters, stale effect-chain anchors and the unread capability flags.

The QA scripts share one keyless guard and readiness wait, the session
harness reuses the strict harness's browser flags and block list, and the
harness honours QA_ANGLE and QA_RESERVED_PORTS. The bikeshare fixture
keeps only what its scenario reads. The docs name the engine picker where
it is (VISUAL PRESETS) and drop dated run results.

No behaviour changes on either engine. Navara layer renderer lines fall
from 189 to 0 and viewer lines from 891 to 849.

scripts/main-chunk-baseline.json

@@ -1,6 +1,6 @@
 {
   "gzipBytes": 2066560,
   "allowanceBytes": 20666,
-  "measuredAt": "HEAD 47d63128 with the layer displays loaded through import() (src/app/layers/displays.js), keyless build (GOOGLE_MAPS_API_KEY and CESIUM_ION_TOKEN empty), entry index-DEjtUM5w.js, 6 322 899 bytes, gzip level 9; HEAD 47d63128 itself measured 2 113 641 and the merge of main 92c8f8d9 2 090 274",
+  "measuredAt": "Keyless production build with dynamically loaded layer displays",
   "allowance": "1% of the baseline; growth past it fails npm run check:main-chunk until the baseline is raised on purpose"
 }