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/ProjectSession.ts

@@ -13,7 +13,11 @@ export class ProjectSession {
    * `beforeSwitch` runs before a different project is loaded or the current one is deleted –
    * a run in progress has to end first, since it holds a copy of the project being replaced.
    */
-  constructor(private readonly state: EditorState, private readonly store: ProjectStore, private readonly beforeSwitch: () => void) {}
+  constructor(
+    private readonly state: EditorState,
+    private readonly store: ProjectStore,
+    private readonly beforeSwitch: () => void,
+  ) {}
 
   /** Opens the project named in the URL, else the first one on the server, else a new one. */
   async boot(): Promise<void> {
@@ -25,7 +29,9 @@ export class ProjectSession {
       }
       await this.openFirstOrCreate();
     } catch (error) {
-      this.state.setNotice(`Could not load project: ${error instanceof Error ? error.message : String(error)}`);
+      this.state.setNotice(
+        `Could not load project: ${error instanceof Error ? error.message : String(error)}`,
+      );
     }
   }
 
@@ -69,10 +75,14 @@ export class ProjectSession {
           label: 'Delete this project…',
           danger: true,
           onSelect: () =>
-            new Dialog(`Delete project "${this.state.project.name}"?`, 'All assets and scenes are removed permanently.', [
-              { label: 'Cancel' },
-              { label: 'Delete', danger: true, onClick: () => void this.deleteCurrent() },
-            ]).openCentered(),
+            new Dialog(
+              `Delete project "${this.state.project.name}"?`,
+              'All assets and scenes are removed permanently.',
+              [
+                { label: 'Cancel' },
+                { label: 'Delete', danger: true, onClick: () => void this.deleteCurrent() },
+              ],
+            ).openCentered(),
         },
       ];
       new Menu(items).openBelow(anchor);
@@ -85,7 +95,8 @@ export class ProjectSession {
       label: scene.id === this.state.project.activeSceneId ? `● ${scene.name}` : scene.name,
       onSelect: () => this.state.execute(new SetActiveSceneCommand(scene.id)),
     }));
-    if (items.length === 0) items.push({ label: 'No scenes – create one in Assets', onSelect: () => {}, disabled: true });
+    if (items.length === 0)
+      items.push({ label: 'No scenes – create one in Assets', onSelect: () => {}, disabled: true });
     new Menu(items).openBelow(anchor);
   }
 }