feat(core): one rect morph for touch presentations that grow out of a source rect

.changeset/motion-rect-morph.md

@@ -0,0 +1,7 @@
+---
+'@astryxdesign/core': patch
+---
+
+[chore] Internal: the rect morph, one way for a touch presentation to grow out of a source rect and shrink back into it. `createRectMorph` presents an element along a path (`lerpPath`, `edgeGrowPath`) and dismisses it back on a copy or on itself, each continuing the other from the rect on screen. A motion a tap or a key starts plays a theme duration and easing; a gesture's release plays a spring from its velocity. Reduced Motion is left to the animator. `timedProgressCurve` joins the progress helpers. Not exported from the package entry point; no component uses it yet.
+
+@vjeux

docs/architecture/react-component-runtime.md

@@ -198,7 +198,9 @@ those contracts.
   change and moves shifted content with a compositor-only translate played
   through the shared rectangle morph (`architecture:layer-runtime` INV15;
   `spec:AST-094` FR5) once Core has that morph; until then, the module plays
-  its own compositor translate. It never animates height. Its walk visits only
+  its own compositor translate. (Implementation gap: Core has the shared
+  rectangle morph, but the size-change glide still plays its own compositor
+  translate.) It never animates height. Its walk visits only
   the changed element's ancestors up to the area and the element siblings on
   either side at each of their levels, through `parentElement`,
   `nextElementSibling` and `previousElementSibling`, descending only into an

packages/core/src/motion/README.md

@@ -39,6 +39,7 @@ roles through `resolveMotion`.
 | `bezier.ts`                                      | Cubic-bézier timing functions (Core Animation's named curves).                                                                                                       |
 | `animator.ts`                                    | Compositor animator: springs, coasts and any closed-form curve compiled to Web Animations, read back analytically.                                                   |
 | `morphPath.ts`                                   | The rect an element shows at each progress of a grow-out presentation: a straight line, a popover’s edge growth, and the curves that put it there.                   |
+| `rectMorph.ts`                                   | Grow out of a source rect and shrink back into it along a path: present and dismiss, each continuing the other from the rect on screen.                              |
 | `progress.ts`                                    | A spring's progress, one curve mapped from another (companions, clamped ranges), the velocity that continues a motion.                                               |
 | `presentation.ts`                                | Where each moving element is drawn relative to where the engine hit-tests it, reported by the animator while translate runs; read by the gesture host at touch-down. |
 | `reducedMotionPlan.ts`                           | The animator's Reduce Motion planner: what one call becomes, a cross-fade whose travel lands while transparent or at once.                                           |

packages/core/src/motion/__tests__/motionBundle.ts

@@ -9,6 +9,8 @@
  */
 
 export {createMotionAnimator} from '../animator';
+export {progressCurve} from '../progress';
+export {createRectMorph, edgeGrowPath, lerpPath} from '../rectMorph';
 export {solveSpring, toSpring} from '../spring';
 export {registerSpringsTable, springs} from '../uikit/springs';
 export {motionRoleOf} from '../roles';