Cut duplicated and dead code across the engines, the layers and the QA scripts

- src/geo drops the ported debug argument checks and the tests that
  bitExact already covers; package boundaries accept a directory entry,
  so src/geo/ is listed once per group.
- Cesium no longer carries movers and lines nobody draws with: they are
  optional engine capabilities. The fake engine and the Cesium camera use
  the shared cameraMath; unused contract tables, clock.ticked, the
  'finest' surface detail and Navara click statistics are gone.
- ALPR keeps one overlay core and one presentation model for both
  engines, bikeshare one station bookkeeping, the Navara ground effects
  one definition helper; image atlases, view centres, mover banks and
  colours are shared.
- The legacy switch route, the clock offset and rate controls and other
  unused exports are removed.
- The acceptance runs the Navara draw, geo import and scope checks;
  scenarios use the harness switch and page helpers; the main chunk
  check keeps the size budget only and runs once in CI.

scripts/qa-vessel-datum.mjs

@@ -19,7 +19,7 @@
  *   node scripts/qa-vessel-datum.mjs --ports rotterdam --url http://localhost:4173
  *   node scripts/qa-vessel-datum.mjs --engine navara --url 'http://localhost:PORT/?qaFeed=vessels:fixture'
  *
- * --engine cesium|navara (phase 3): the engine-neutral path on either engine,
+ * --engine cesium|navara: the engine-neutral path on either engine,
  * through window.__godsEyeView.engine and the QA probe (layers.drawn: each
  * chevron's drawn position and depth-test flag) instead of the Cesium
  * viewer's primitives; the URL gets ?engine=. Without it, as before.