Merge origin/main into german/navara

Brings in 190 commits from main. Integration on the engine contract:

- News and Shipwrecks draw, pick and keep their selection through the
  contract and shared map markers, so they follow engine switches.
- Aircraft tracking uses main's segmented trails with contract frame
  numbers.
- Decoded weather tiles move into the Cesium adapter and are injected
  through the renderer registry; Navara hides those sources on globe
  surfaces (docs/KNOWN-ISSUES.md).
- Street-vehicle GPU depth occlusion stays Cesium-only; Navara keeps
  the geometric visibility checks (docs/KNOWN-ISSUES.md).
- Transit includes the heading-neutral atlas icons.

scripts/qa-all-layer-switches.mjs

@@ -286,6 +286,12 @@ const soakRuns = quick
 const longRun = quick ? '--swaps=100' : '--swaps=500';
 // label, script, layers, extra arguments, timeout in seconds.
 const runs = [
+  [
+    'switch-equals-cold-start--markers',
+    'switch-equals-cold-start',
+    ['news', 'shipwrecks'],
+    ['--group=markers'],
+  ],
   [
     'switch-equals-cold-start--aircraft',
     'switch-equals-cold-start',