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>

coredocs/guide/render-graphs.md

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+# Render graphs from raw JavaScript
+
+## Wire encoder
+
+`compile-graph` does not accept JSON. It accepts one S-expression: `(yawn-graph 1 VALUE)`. Objects are `(object (field KEY VALUE)...)`; arrays are `(array VALUE...)`. Strings use JSON quoting. Bare `true`, `false`, `null`, and JSON numbers become their corresponding values; other bare atoms become strings. Quote all object keys and application strings to avoid ambiguity.
+
+```js
+function graphValue(value) {
+  if (value === null) return "null";
+  if (Array.isArray(value)) return `(array ${value.map(graphValue).join(" ")})`;
+  if (typeof value === "object") {
+    return `(object ${Object.entries(value).map(([key, item]) =>
+      `(field ${JSON.stringify(key)} ${graphValue(item)})`
+    ).join(" ")})`;
+  }
+  if (typeof value === "string") return JSON.stringify(value);
+  if (typeof value === "boolean") return String(value);
+  if (typeof value === "number" && Number.isFinite(value)) return String(value);
+  throw new TypeError("graph contains an unsupported value");
+}
+function encodeGraph(graph) {
+  return `(yawn-graph 1 ${graphValue(graph)})`;
+}
+```
+
+Duplicate object fields, malformed/trailing expressions, the wrong tag/version, and empty lists fail with `GRAPH_WIRE`.
+
+## Minimal complete triangle
+
+This graph needs no row arrays. `canvas` is a special attachment and fragment target format; do not declare it as a texture.
+
+```js
+const triangle = {
+  id: "raw-triangle",
+  pipelines: {
+    render: [{
+      id: "triangle-pipeline",
+      code: `
+        struct Out { @builtin(position) position: vec4f, @location(0) color: vec3f }
+        @vertex fn vertex(@builtin(vertex_index) i: u32) -> Out {
+          var positions = array<vec2f, 3>(vec2f(0.0, 0.7), vec2f(-0.7, -0.7), vec2f(0.7, -0.7));
+          var colors = array<vec3f, 3>(vec3f(1,0,0), vec3f(0,1,0), vec3f(0,0,1));
+          var out: Out; out.position = vec4f(positions[i], 0, 1); out.color = colors[i]; return out;
+        }
+        @fragment fn fragment(in: Out) -> @location(0) vec4f { return vec4f(in.color, 1); }
+      `,
+      vertex: { entry: "vertex", buffers: [] },
+      fragment: { entry: "fragment", targets: [{ format: "canvas" }] },
+    }],
+  },
+  passes: [{
+    id: "triangle",
+    type: "render",
+    pipeline: "triangle-pipeline",
+    color: [{ resource: "canvas", load: "clear", store: "store", clear: [0.02, 0.02, 0.03, 1] }],
+    draw: { vertices: 3, instances: 1 },
+  }],
+};
+
+const id = await request("compile-graph", { serialized: encodeGraph(triangle) });
+await request("switch-loadout", { id }); // activates and requests the first frame
+```
+
+## Ordering and resources
+
+`passes` declaration order is only a tie-breaker. Each pass's `after` IDs form a dependency DAG; compilation performs a stable-like first-ready topological ordering. Missing dependency → `GRAPH_DEPENDENCY`; cycle → `GRAPH_CYCLE`. Unused resources and pipelines are removed. Used textures receive lifetime slots; compatible transient textures with non-overlapping lifetimes can alias. Therefore do not expect an unused declaration to exist at runtime.
+
+Adjacent compatible render passes may execute in one render pass/bundle. To merge they need matching attachments/sample count, previous `store`, next `load`, matching depth behavior, and the next pass must not bind its attachment as an input. Compute passes remain separate.
+
+Buffers map an entire named SAB row array into a GPU buffer. Bindings are grouped by `group` and use the pipeline's automatically inferred WGSL layout. A binding resource ID may identify a buffer, texture view, or sampler. Vertex/index bindings must identify buffers. Color/depth attachments identify declared textures or special `canvas`. The WGSL declarations, usage flags, offsets, sizes, target formats, and attachment formats must agree; WebGPU validation failures can otherwise surface as generic worker/core errors.
+
+See [Graph schema](/reference/graph-schema) for every field and default.