feat(web): close remaining editor, layout and persistence gaps

- Area headers get a per-area editor switcher backed by a shared
  AreaEditorContext; Preferences can hide it.
- Animation camera area is a real navigable viewport aligned to the
  scene camera; Graph Editor adds channel selection, keyframe drag/
  insert/delete and interpolation.
- Geometry Nodes node locations round-trip through the native writer
  and reader, so saved graphs keep their layout.
- Texture Paint can make linked library images local via a new native
  makeImageLocal command before packing strokes.
- Compositor IMAGE and Render Layers nodes now persist to Main and
  execute against packed images / the last PBR render.
- Spreadsheet row cap raised to 250k; Outliner gains Ctrl+A and arrow/
  Home/End navigation.

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

web/protocol/compositor-commands.ts

@@ -1,4 +1,4 @@
-import type { CompositorGraphIR, CompositorLinkIR, CompositorNodeIR, CompositorNodeType } from "./compositor";
+import type { CompositorGraphIR, CompositorLinkIR, CompositorNodeIR, CompositorNodeType, CompositorResourceIR } from "./compositor";
 
 function clone(graph: CompositorGraphIR): CompositorGraphIR {
   return structuredClone(graph);
@@ -62,6 +62,18 @@ export const compositorCommands = Object.freeze({
     if (node) node.properties = { ...node.properties, [key]: value };
     return next;
   },
+  upsertResource(graph: CompositorGraphIR, resource: CompositorResourceIR): CompositorGraphIR {
+    const next = clone(graph);
+    const index = next.resources.findIndex((candidate) => candidate.id === resource.id);
+    if (index >= 0) next.resources[index] = { ...resource };
+    else next.resources.push({ ...resource });
+    return next;
+  },
+  removeResource(graph: CompositorGraphIR, resourceId: string): CompositorGraphIR {
+    const next = clone(graph);
+    next.resources = next.resources.filter((resource) => resource.id !== resourceId);
+    return next;
+  },
   setOutput(graph: CompositorGraphIR, nodeId: string): CompositorGraphIR {
     const next = clone(graph);
     if (next.nodes.find((node) => node.id === nodeId)?.type !== "COMPOSITE") return graph;