feat(directions): keyless A→B directions with turn-by-turn steps and FLY (#564)

Supersedes #219 by @spcpza, ported onto the current component layout with fixes from review.

Verified before merge: format, package boundaries, unit suite, build, and the browser tracking suite; a browser harness for the change where one applies; adversarial review applied.

Co-authored-by: spcpza <[email protected]>

src/data/directions.js

@@ -0,0 +1,69 @@
+/**
+ * @module directions
+ * @description Service bundle for the Directions layer.
+ *
+ * The layer itself lives in `src/layers/directions/`, which imports nothing
+ * but Cesium and the pure step formatter. This module is the one place that
+ * names the application's shared services — the render governor, sprite order,
+ * the pick registry, the world overlay, the annotation material, the camera
+ * verbs, the shared ground floor and the pointer arbiter — and it re-exports
+ * the layer's pure helpers for the tests and the share-link code.
+ */
+
+import * as render from '../renderGovernor.js';
+import * as sprites from './spriteOrder.js';
+import * as picking from './pickRegistry.js';
+import * as scenePick from './scenePick.js';
+import * as overlays from '../overlays/worldOverlay.js';
+import * as annotations from '../annotations/worldAnnotationRenderer.js';
+import * as camera from '../cameraVerbs.js';
+import * as ground from './groundFloor.js';
+import * as input from './inputOwnership.js';
+import { createDirectionsLayer } from '../layers/directions/index.js';
+
+/** The shared scene owners every Directions instance runs on. */
+export const directionsServices = Object.freeze({
+  render,
+  sprites,
+  picking,
+  scenePick,
+  overlays,
+  annotations,
+  camera,
+  ground,
+  input,
+});
+
+/** Construct one Directions layer over the application scene owners. */
+export function createApplicationDirectionsLayer() {
+  return createDirectionsLayer({ services: directionsServices });
+}
+
+export {
+  DEFAULT_DIRECTIONS_MODE,
+  DIRECTIONS_MODES,
+  DIRECTIONS_POINTER_OWNER,
+  DIRECTIONS_ROUTE_COLOR,
+  DIRECTIONS_STEP_OVERLAY_SOURCE_ID,
+  DIRECTIONS_STEP_OVERLAY_SOURCE_OPTIONS,
+  FLIGHT_PROGRESS_MS,
+  POINTER_TOOL_EXITS,
+  STEP_ANCHOR_DEADLINE_MS,
+  STEP_ANCHOR_FAST_ATTEMPTS,
+  STEP_ANCHOR_RETRY_MS,
+  STEP_ANCHOR_SLOW_RETRY_MS,
+  createDirectionsLayer,
+  createDirectionsStepOverlayEntry,
+  directionsRequestUrl,
+  directionsRowControls,
+  directionsStats,
+  directionsStepCopy,
+  directionsStepList,
+  normalizeDirectionsParams,
+  normalizeRoutePayload,
+  pointerBlockedMessage,
+  stepAnchorDelayMs,
+  stepIndexAtDistance,
+  stepMarkerHeightM,
+  stepMarkerIndices,
+} from '../layers/directions/index.js';