Transform: scale, rotation and mirror as properties, world transform as a matrix chain, oriented colliders (#76)

Four new rows on sprite, text, collider and container (block TRANSFORM):
scale, rotation in degrees clockwise, mirrorX, mirrorY. As properties they
get override/reset/apply, loading of old projects, write-back after play and
the Properties node for free; camera and behavior have none.

The hierarchy composes T*R*S per level (composeAlongChain replaces
sumAlongChain), so children rotate and scale with their parent. Reparenting
and grouping keep the look (carriedTransform). Drawing goes through
placeNode, the gizmo is a polygon, cull and objectRect use the AABB, drags
are computed in the parent's system.

Colliders are oriented boxes: SAT for box/box, box-circle in the box frame;
exitDistance replaces axisSeparation/axisCorrection, moveAndSlide moves along
the object's own axes.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/core/serialize.test.ts

@@ -61,6 +61,10 @@ describe('serialize', () => {
     expect(project.assets[1]!.name).toBe('sprite');
     expect(project.assets[1]!.props).toEqual({
       enabled: true,
+      scale: 1,
+      rotation: 0,
+      mirrorX: false,
+      mirrorY: false,
       width: 10,
       height: 100,
       color: 0xffffff,