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>

README.md

@@ -37,7 +37,7 @@ npm run build        # writes dist/ and regenerates index.html; the folder is wh
 The browser suite and the three example games need a machine with a GPU:
 
 ```bash
-node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 742 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 758 checks (GM_STEPS=20 for one step)
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs
 node tools/seed-tetris.mjs && node tools/smoke-tetris.mjs
 node tools/seed-actor.mjs && node tools/smoke-actor.mjs