feat(globe): implement the engine on Cesium

createCesiumEngine wraps an existing viewer without changing it: camera, picker, projector, frames, render (through the render governor), surface, input, credits and maps, with geo values out and Cesium values in at the boundary. Map and surface code is shared with src/maps and services/groundSnap instead of copied. scripts/qa-globe-contract.mjs runs the contract suite against the engine in headless Chrome; the camera-events check now waits for the previous move to end, as Cesium's moveStart marks a move from rest.

src/globe/cesium/render.js

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+// GlobeRender on the app's render governor, which owns Cesium's
+// requestRenderMode and maximumRenderTimeChange; the engine only takes a
+// hold under its own owner id.
+
+import {
+  governorRequestRender,
+  holdContinuousRender,
+  releaseContinuousRender,
+} from '../../renderGovernor.js';
+
+export const RENDER_OWNER = 'globe-engine';
+
+/**
+ * @param {Cesium.Viewer} viewer
+ * @param {{ requestRender?: (reason: string) => void }} [options]
+ * @returns {{ render: import('../contract.js').GlobeRender, destroy: () => void }}
+ */
+export function createCesiumRender(
+  viewer,
+  { requestRender = governorRequestRender } = {},
+) {
+  let held = false;
+  const render = {
+    request() {
+      requestRender(RENDER_OWNER);
+    },
+    setContinuous(enabled) {
+      held = Boolean(enabled);
+      if (held) holdContinuousRender(RENDER_OWNER);
+      else releaseContinuousRender(RENDER_OWNER);
+    },
+    // The scene's real mode: another owner's hold keeps it continuous.
+    isContinuous: () => viewer.scene.requestRenderMode === false,
+  };
+  return {
+    render,
+    destroy() {
+      if (held) render.setContinuous(false);
+    },
+  };
+}