Add a Navara HD renderer choice, release a parked engine after three minutes, and cut Navara's memory

Navara now draws at CSS pixels without MSAA, like Cesium; Navara HD keeps the device pixel ratio and MSAA 4. Only one Navara variant is ever kept. A parked engine is released after three minutes and its WebGL context is lost. Three leaks that kept a released Navara alive are fixed, the canvas context drops its unused antialias buffer, cloud shadows use two 256 px cascades, and the tile cache is budgeted from the screen buffers.

scripts/qa-all-layer-switches.mjs

@@ -362,6 +362,8 @@ const runs = [
   ['strict-rapid-switch', 'strict-rapid-switch', []],
   ['strict-hidden-switch', 'strict-hidden-switch', []],
   ['strict-context-loss', 'strict-context-loss', []],
+  ['strict-parked-release', 'strict-parked-release', []],
+  ['strict-navara-hd', 'strict-navara-hd', []],
   ['strict-failure-matrix', 'strict-failure-matrix', [], [], 600],
   ['strict-cold-chunks', 'strict-cold-chunks', []],
   ['strict-prod-smoke', 'strict-prod-smoke', []],