Build Rust render graph core

Keep hot render state in a generic shared SOA arena and use worker messages only for allocation, graph compilation, loadout changes, and render pacing. Compile external S-expression graphs into upfront WebGPU resources, transient aliases, and reusable render bundles.

Amp-Thread-ID: https://ampcode.com/threads/T-01a01380-b478-77d0-84a0-102880a5c5ae
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

core/render_graph/store.rs

@@ -0,0 +1,62 @@
+use std::collections::HashMap;
+
+use crate::gpu::Wgpu;
+use crate::gpu_resource::GpuResources;
+use crate::graph::RenderGraph;
+use crate::render_data::RenderData;
+
+pub struct Loadout {
+    pub graph: RenderGraph,
+    pub resources: GpuResources,
+}
+
+#[derive(Default)]
+pub struct Store {
+    graphs: HashMap<String, RenderGraph>,
+    active: Option<Loadout>,
+}
+
+impl Store {
+    pub fn save(&mut self, graph: RenderGraph) -> String {
+        let id = graph.id.clone();
+        self.graphs.insert(id.clone(), graph);
+        id
+    }
+
+    pub fn switch(&mut self, id: &str, gpu: &Wgpu, data: &RenderData) -> Result<(), String> {
+        let graph = self.graphs.get(id).ok_or("GRAPH_UNKNOWN")?.clone();
+        let resources = GpuResources::activate(&graph, gpu, data)?;
+        self.active = Some(Loadout { graph, resources });
+        Ok(())
+    }
+
+    pub fn active_mut(&mut self) -> Option<&mut Loadout> {
+        self.active.as_mut()
+    }
+
+    pub fn uses_rows(&self, name: &str) -> bool {
+        self.active.as_ref().is_some_and(|active| {
+            active
+                .graph
+                .resources
+                .buffers
+                .iter()
+                .any(|buffer| buffer.array == name)
+        })
+    }
+
+    pub fn refresh_rows(
+        &mut self,
+        name: &str,
+        gpu: &Wgpu,
+        data: &RenderData,
+    ) -> Result<(), String> {
+        if !self.uses_rows(name) {
+            return Ok(());
+        }
+        let graph = self.active.as_ref().unwrap().graph.clone();
+        let resources = GpuResources::activate(&graph, gpu, data)?;
+        self.active = Some(Loadout { graph, resources });
+        Ok(())
+    }
+}