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/ui-schema.ts

@@ -19,6 +19,7 @@ export type EditorType =
   | "Properties"
   | "Timeline"
   | "Dope Sheet"
+  | "Graph Editor"
   | "Image Editor"
   | "Render Result"
   | "Shader Editor"