feat(globe): add the engine contract and its test suite

src/globe/contract.js defines the engine-neutral GlobeEngine capabilities
(JSDoc), createEngineEvent with Cesium.Event semantics and
assertGlobeEngine. src/globe/testing adds a geo-based fake engine for shell
tests and an engine-agnostic contract suite that the fake passes in Node.
check-import-directions keeps the contract free of cesium, three and
@navaramap, and each engine directory free of the other engine.

scripts/format-scope.json

@@ -719,6 +719,8 @@
   "scripts/module-analysis.mjs",
   "scripts/check-import-directions.mjs",
   "src/tooling/importDirections.test.mjs",
+  "src/globe/contract.test.mjs",
+  "src/globe/testing/fakeEngine.test.mjs",
   "src/sources/reference.js",
   "src/sources/reference.test.mjs",
   "src/search/nominatim.js",