Add ESLint and Prettier, and close the node test gaps

Tooling:
- Prettier as the single formatting authority (110 columns, single quotes,
  measured against the existing style); Markdown excluded because table-cell
  padding turns the README glossary into 1000-character lines.
- Type-aware ESLint ending in eslint-config-prettier, so a rule always means
  "this is a bug", never "this looks different".
- .editorconfig and an `npm run check` that runs typecheck, lint, format and
  tests in one go.

Findings fixed on the first run: three more duplicate imports, four
String(unknown) calls (parameter types narrowed instead of casts), two dead
initialisers, two redundant casts, a console.log for a real error. Two
warnings were false here and are disabled with a reason in place.

Tests 132 -> 269:
- node-catalog.test.ts covers every node with a run(), with a guard that fails
  when a new node has no row.
- behavior-events.test.ts covers the ten event nodes through a running World,
  checking timing rather than existence.
- Input's state machine (press/release/releaseAll) is reachable without DOM
  events now; the DOM handlers are thin adapters.

Compare fell back to == without a configured operator although the schema
default is <; aligned.

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

src/editor/panels/AssetPanel.ts

@@ -13,12 +13,21 @@ export class AssetPanel extends Panel {
   private readonly list = new ListView();
   private readonly scroll = new ScrollContainer();
 
-  constructor(private readonly state: EditorState, private readonly placementPoint: () => Vec2) {
+  constructor(
+    private readonly state: EditorState,
+    private readonly placementPoint: () => Vec2,
+  ) {
     super({ title: 'Assets', padding: 0, gap: 0 });
     this.minWidth = 160;
 
     const add = new Button('+', { variant: 'ghost', width: 28 });
-    add.onClick = () => new Menu(ASSET_TYPES.map((type) => ({ label: ASSET_TYPE_LABELS[type], onSelect: () => this.createAsset(type) }))).openBelow(add);
+    add.onClick = () =>
+      new Menu(
+        ASSET_TYPES.map((type) => ({
+          label: ASSET_TYPE_LABELS[type],
+          onSelect: () => this.createAsset(type),
+        })),
+      ).openBelow(add);
     this.header.add(add);
 
     this.list.emptyText = 'No assets – press +';
@@ -81,9 +90,17 @@ export class AssetPanel extends Panel {
     if (!asset) return;
     const items: MenuItem[] = [];
     if (asset.type === 'scene') {
-      items.push({ label: 'Set as active scene', onSelect: () => this.state.execute(new SetActiveSceneCommand(id)), disabled: this.state.project.activeSceneId === id });
+      items.push({
+        label: 'Set as active scene',
+        onSelect: () => this.state.execute(new SetActiveSceneCommand(id)),
+        disabled: this.state.project.activeSceneId === id,
+      });
     } else {
-      items.push({ label: 'Place in scene', onSelect: () => this.place(id), disabled: !this.state.activeScene });
+      items.push({
+        label: 'Place in scene',
+        onSelect: () => this.place(id),
+        disabled: !this.state.activeScene,
+      });
     }
     items.push({ label: 'Delete…', danger: true, onSelect: () => confirmDeleteAsset(this.state, id) });
     new Menu(items).open(x, y);

src/editor/panels/HierarchyPanel.ts

@@ -49,7 +49,10 @@ export class HierarchyPanel extends Panel {
 
     state.on('project', () => this.refresh());
     // A different project brings different objects – start folded again.
-    state.on('load', () => { this.expanded.clear(); this.refresh(); });
+    state.on('load', () => {
+      this.expanded.clear();
+      this.refresh();
+    });
     state.on('selection', () => (this.revealSelection() ? this.refresh() : this.syncSelection()));
     this.refresh();
   }
@@ -88,13 +91,31 @@ export class HierarchyPanel extends Panel {
     const selected = state.selectedObjectIds.includes(id) ? state.selectedObjectIds : [id];
     const many = selected.length > 1;
     new Menu([
-      { label: 'Select asset', onSelect: () => object && state.select({ kind: 'asset', assetId: object.assetId }) },
-      { label: 'Add collider', disabled: !type || type === 'collider' || many, onSelect: () => addCollider(state, scene.id, id) },
-      { label: many ? `Create container from ${selected.length} objects` : 'Create container', onSelect: () => createContainer(state, scene.id, selected) },
-      { label: 'Unparent (move to top level)', disabled: !object?.parentId || many, onSelect: () => state.execute(new SetParentCommand(scene.id, id, '')) },
+      {
+        label: 'Select asset',
+        onSelect: () => object && state.select({ kind: 'asset', assetId: object.assetId }),
+      },
+      {
+        label: 'Add collider',
+        disabled: !type || type === 'collider' || many,
+        onSelect: () => addCollider(state, scene.id, id),
+      },
+      {
+        label: many ? `Create container from ${selected.length} objects` : 'Create container',
+        onSelect: () => createContainer(state, scene.id, selected),
+      },
+      {
+        label: 'Unparent (move to top level)',
+        disabled: !object?.parentId || many,
+        onSelect: () => state.execute(new SetParentCommand(scene.id, id, '')),
+      },
       { label: 'Expand all', onSelect: () => this.expandAll() },
       { label: 'Collapse all', onSelect: () => this.collapseAll() },
-      { label: many ? `Remove ${selected.length} objects from scene` : 'Remove from scene', danger: true, onSelect: () => removeObjects(state, scene.id, selected) },
+      {
+        label: many ? `Remove ${selected.length} objects from scene` : 'Remove from scene',
+        danger: true,
+        onSelect: () => removeObjects(state, scene.id, selected),
+      },
     ]).open(x, y);
   }
 

src/editor/panels/Toolbar.ts

@@ -34,7 +34,10 @@ export class Toolbar extends HStack {
   private readonly notice: Label;
   private readonly fps: Label;
 
-  constructor(private readonly state: EditorState, actions: ToolbarActions) {
+  constructor(
+    private readonly state: EditorState,
+    actions: ToolbarActions,
+  ) {
     super({ gap: Theme.gap, padding: Theme.padding, align: 'center' });
     this.minHeight = Theme.controlHeight + Theme.padding * 2;
     this.addChildAt(this.bg, 0);
@@ -53,7 +56,10 @@ export class Toolbar extends HStack {
     this.add(new Spacer(Theme.padding));
 
     this.add(new Label('Scene', { style: 'muted' }));
-    this.sceneButton = new Button('—', { width: 160, onClick: () => actions.openSceneMenu(this.sceneButton) });
+    this.sceneButton = new Button('—', {
+      width: 160,
+      onClick: () => actions.openSceneMenu(this.sceneButton),
+    });
     this.add(this.sceneButton);
     this.add(new Spacer(Theme.padding));
 
@@ -63,7 +69,11 @@ export class Toolbar extends HStack {
     this.add(this.redoButton);
 
     this.add(new Spacer(), 1);
-    this.playButton = new Button('▶  Play', { variant: 'primary', width: 110, onClick: () => actions.togglePlay() });
+    this.playButton = new Button('▶  Play', {
+      variant: 'primary',
+      width: 110,
+      onClick: () => actions.togglePlay(),
+    });
     this.add(this.playButton);
     this.add(new Spacer(), 1);