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/ui/FocusManager.ts

@@ -91,10 +91,6 @@ export class FocusManager {
       }
     }
   }
-
-  destroy(): void {
-    window.removeEventListener('keydown', this.onKeyDown);
-  }
 }
 
 function isAttached(node: Container, root: Container): boolean {

src/ui/KeyboardBridge.ts

@@ -88,11 +88,6 @@ export class KeyboardBridge {
     if (document.activeElement === this.input) this.input.setSelectionRange(selectionStart, selectionEnd);
   }
 
-  /** The field learns about it through the usual `onBridgeInput` sync. */
-  selectAll(): void {
-    this.input.select();
-  }
-
   /** Ignored when another field attached meanwhile, so a late blur cannot steal it. */
   detach(target: TextEditTarget): void {
     if (this.target !== target) return;

src/ui/Theme.ts

@@ -26,7 +26,7 @@ export const Theme = {
     border: 0x383c46,
     control: 0x16181d,
     controlHover: 0x1e2127,
-    controlActive: 0x2a2e37,
+    controlActive: 0x16181d,
     accent: 0x4c8dff,
     accentText: 0xffffff,
     text: 0xe6e8ee,

src/ui/widgets/ColorField.ts

@@ -57,11 +57,6 @@ export class ColorField extends Widget {
     this.addChild(this.row);
   }
 
-  /** The last valid color: an invalid hex being typed does not change it. */
-  get value(): number {
-    return this.color;
-  }
-
   /** Model → view update: refreshes the hex text and an open picker without firing callbacks. */
   setValue(color: number): void {
     if (color === this.color) return;

src/ui/widgets/ListView.ts

@@ -92,10 +92,6 @@ export class ListView extends Widget {
     this.onPointerRelease(() => this.onDragEnd());
   }
 
-  get selected(): string | null {
-    return this.selectedId;
-  }
-
   /**
    * Rebuilds all rows. The selection survives when its id is still present and is dropped
    * silently otherwise; highlights are kept as they are (the owner refreshes them).

src/ui/widgets/NumberField.ts

@@ -85,11 +85,6 @@ export class NumberField extends TextField {
     });
   }
 
-  /** The clamped numeric value; while typing, the last valid parse of the text. */
-  get number(): number {
-    return this.numeric;
-  }
-
   /** The one place the value becomes text, so every path honours `decimals`. */
   private get display(): string {
     return formatNumber(this.numeric, this.decimals);