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>

README.md

@@ -96,13 +96,23 @@ other). They are editor symbols: green outlines in edit mode, invisible in play
 
 Play runs a `CollisionSystem` (`src/runtime/systems/CollisionSystem.ts`) before the behaviors:
 every frame it tests all collider pairs (world positions applied; touching edges do not count)
-and sorts them into *enter*, *stay* and *exit*. **Detection only** – nothing is pushed apart
-yet. A behavior receives `On collision enter/stay/exit` for the colliders of its **owner**
-(its parent; itself when top-level): the outputs are `other` (the other body), `other collider`
+and sorts them into *enter*, *stay* and *exit*. Detection never pushes anything apart. A
+behavior receives `On collision enter/stay/exit` for the colliders of its **owner** (its
+parent; itself when top-level): the outputs are `other` (the other body), `other collider`
 and `collider` (the own one). `Is touching(a, b)` answers the same question on demand – an
 object stands for its collider children, a collider for itself. The geometry lives in
 `src/core/properties/collider.ts` so editor and runtime agree on it.
 
+**Blocking** is opt-in per movement: the `Move and slide` node (same inputs as `Move`) moves
+an object one axis at a time and, after each axis, pushes its *solid* colliders back to just
+touch any solid collider they ran into – so the other axis still moves and the object slides
+along walls. Its `blocked x` / `blocked y` outputs tell which axes hit. A collider with
+**Trigger (no blocking)** enabled (`isTrigger`, drawn amber instead of green) still produces
+collision events but never blocks. Pairs that already overlapped before the step are left
+alone, so an object that starts inside a wall can leave it and stacked objects never jolt apart.
+Colliders of the moving object and of anything parented under it travel with it and cannot
+block it. Plain `Move` / `Set position` ignore colliders entirely.
+
 ## Stack
 
 - **PixiJS v8** – rendering and pointer events. No game engine; runtime systems live in `src/runtime/`.