Render only when shared state changes

Add shared-data and bundle invalidation signals, and have handles publish them automatically for SAB and graph mutations.

Document the raw core worker protocol in a dedicated VitePress site and simplify the glTF import and picking example.

Amp-Thread-ID: https://ampcode.com/threads/T-01a01ff8-b91f-724f-8952-f07c6b5042fd
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

README.md

@@ -8,7 +8,7 @@ JSO or FXNode → AST → S-expression → worker messages → Rust/WebGPU
 any thread → direct shared row writes ─────────────┘
 ```
 
-The arena starts with only one eight-float `info` row for frame timing and direct SAB render skipping. Messages create or delete other `{ name, rows, stride, format }` arrays, allocate named slots, compile graphs, switch loadouts, and control render pacing. Existing render data is changed by writing `f32`, `u32`, or `i32` rows directly. Allocations are 64-byte aligned, row strides are multiples of 16 bytes, and compatible non-overlapping transient textures share physical allocations.
+The arena starts with only one eight-float `signals` row for frame timing and render invalidation. Messages create or delete other `{ name, rows, stride, format }` arrays, allocate named slots, compile graphs, switch loadouts, and control render pacing. Existing render data is changed by writing `f32`, `u32`, or `i32` rows directly, then setting the shared-data dirty signal. Allocations are 64-byte aligned, row strides are multiples of 16 bytes, and compatible non-overlapping transient textures share physical allocations.
 
 WGSL, pipelines, glTF import, and conventional mesh/camera/material handles live in `addons/`; core contains no shader or scene model.
 
@@ -17,3 +17,5 @@ npm start
 ```
 
 This opens the docs. The complete runnable example is at `/playground`.
+
+Run `npm run coredocs` for the raw worker-message, shared-memory, and render-graph reference intended for custom handles, editors, and direct SAB clients.