Consolidate core-v2 modules and move scene logic onto classes

- Merge the small modules into 12 files: shared, choreography,
  navigation, scene/{types,graph,scene}, gesture/{definition,recognizer}.
- SceneGraph now owns the begin/update/commit/cancel history rules as
  methods, with the step helpers as private methods.
- createOriginScene returns a markRaw'd Scene class; operation handles
  are an OperationHandle class instead of inline object literals.
- GestureRecognizer gains static create()/policyFor() factories, absorbing
  the separate policy module.
- Pure helpers used by classes (matchesStart, pointOf, stepSpring,
  composeNodeStyle, nodeEffectLayers, shouldCommit, ...) are exported
  consts so they can be tested directly.
- Add haptics tests showing where navigator.vibrate can be triggered.

Public exports, types, and behavior are unchanged; the differential
suites against main still pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Faarh2Ts6StJPcz2mRiHiR

packages/core-v2/src/shared.ts

@@ -0,0 +1,52 @@
+/** A rectangle measured in viewport CSS pixels. */
+export interface OriginRect {
+  /** Distance from the viewport's top edge in CSS pixels. */
+  top: number;
+  /** Distance from the viewport's left edge in CSS pixels. */
+  left: number;
+  /** Rectangle width in CSS pixels. */
+  width: number;
+  /** Rectangle height in CSS pixels. */
+  height: number;
+}
+
+/** Clamp a value to the inclusive unit range `0..1`. */
+export function clamp01(value: number): number {
+  return Math.max(0, Math.min(1, value));
+}
+
+/** Clamp a value to the inclusive range `min..max`. */
+export function clamp(value: number, min: number, max: number): number {
+  return Math.max(min, Math.min(max, value));
+}
+
+/** Measure an element's viewport bounds as a plain, serializable rectangle. */
+export function measureRect(element: Element): OriginRect {
+  const { top, left, width, height } = element.getBoundingClientRect();
+  return { top, left, width, height };
+}
+
+/** Bounds of the browser window, or a unit rectangle outside a browser. */
+export function windowRect(): OriginRect {
+  const browser = typeof window !== "undefined";
+  return {
+    top: 0,
+    left: 0,
+    width: browser ? window.innerWidth : 1,
+    height: browser ? window.innerHeight : 1,
+  };
+}
+
+/**
+ * Whether animation should resolve immediately.
+ *
+ * True outside a browser, when `requestAnimationFrame` is unavailable, or when
+ * the user prefers reduced motion.
+ */
+export function prefersReducedMotion(): boolean {
+  return (
+    typeof window === "undefined" ||
+    !window.requestAnimationFrame ||
+    Boolean(window.matchMedia?.("(prefers-reduced-motion: reduce)").matches)
+  );
+}