Remove exports and methods nothing uses any more

A reference search over every export and method in src/ found code that
only tests still called, or that was never called at all:

- RemoveSceneObjectCommand: the product only removes through the
  multi-object command; the tests now use that one too.
- NodeRegistry.requireNodeDef: a second function of the same name in
  commands/require.ts raises a CommandError instead of throwing, and is
  the one the product uses. The twin invited the wrong import.
- isTextureAsset, listContainers, AssetTabEditor.show,
  FocusManager.destroy, KeyboardBridge.selectAll and the getters
  ColorField.value, ListView.selected, NumberField.number.

Also: Theme.controlActive now matches the resting control colour, and a
new note asks what editing the graph during play would take.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/commands/require.ts

@@ -62,10 +62,7 @@ export function requireNode(project: Project, assetId: string, nodeId: string):
   return node;
 }
 
-/**
- * `NodeRegistry.requireNodeDef` throws a plain `Error`, which the editor does not catch; a command
- * needs a `CommandError` so an unknown type becomes a notice instead of a crash.
- */
+/** A `CommandError`, so an unknown type becomes a notice instead of a crash. */
 export function requireNodeDef(type: string): NodeDef {
   const def = nodeDef(type);
   if (!def) throw new CommandError(`Unknown node type "${type}"`);

src/core/commands/sceneObjectCommands.ts

@@ -111,12 +111,6 @@ export class RemoveSceneObjectsCommand implements Command {
   }
 }
 
-export class RemoveSceneObjectCommand extends RemoveSceneObjectsCommand {
-  constructor(holderId: string, objectId: string) {
-    super(holderId, [objectId]);
-  }
-}
-
 /**
  * The previous position is read at execution time, so a caller that previewed the move must
  * restore the model before executing.

src/core/graph/NodeRegistry.ts

@@ -111,12 +111,6 @@ export function nodeDef(type: string): NodeDef | undefined {
   return defs.get(type);
 }
 
-export function requireNodeDef(type: string): NodeDef {
-  const def = defs.get(type);
-  if (!def) throw new Error(`Unknown node type "${type}"`);
-  return def;
-}
-
 export function allNodeDefs(): NodeDef[] {
   return [...defs.values()];
 }

src/core/model/Asset.ts

@@ -86,7 +86,3 @@ export type Asset =
 export function isSceneAsset(asset: Asset): asset is SceneAsset {
   return asset.type === 'scene';
 }
-
-export function isTextureAsset(asset: Asset): asset is TextureAsset {
-  return asset.type === 'texture';
-}

src/core/model/Project.ts

@@ -64,7 +64,3 @@ export function findObjectHolder(project: Project, holderId: string): ObjectHold
   const asset = findAsset(project, holderId);
   return asset && isObjectHolder(asset) ? asset : undefined;
 }
-
-export function listContainers(project: Project): ContainerAsset[] {
-  return project.assets.filter((a): a is ContainerAsset => a.type === 'container');
-}