Trigger colliders and Move and slide against solid colliders

- Collider property isTrigger (no blocking, still reports enter/stay/exit)
- Node 'Move and slide' with blocked x/y outputs, axis-wise resolution
- axisSeparation/axisCorrection geometry for box/box, circle/circle, box/circle
- Amber outline for trigger colliders in the viewport
- Demo mover uses Move and slide; E2E step 15b, 7 new unit tests

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

src/ui/Theme.ts

@@ -32,8 +32,9 @@ export const Theme = {
     gizmo: 0x4c8dff,
     /** Behavior symbols and owner links. */
     behavior: 0xb066ff,
-    /** Collider outlines. */
+    /** Collider outlines: solid (blocking) and trigger (events only). */
     collider: 0x4fd18b,
+    trigger: 0xf2c84b,
     /** Node graph: canvas, node chrome, per-category title colors, port colors, live highlight. */
     graphBackground: 0x15171b,
     node: 0x262a32,