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>

tests/core/enabled.test.ts

@@ -6,7 +6,17 @@ import { isHandleEnabled } from '../../src/core/graph';
 import { findAsset, findScene } from '../../src/core/model/Project';
 import { schemaFor } from '../../src/core/properties/PropertySchema';
 import { resolveSceneObjectProps } from '../../src/core/properties/resolve';
-import { fakeHandle, graphEditor, makeBehavior, makeProject, makeSpriteScene, place, roundTrip, runNode, startWorld } from '../helpers';
+import {
+  fakeHandle,
+  graphEditor,
+  makeBehavior,
+  makeProject,
+  makeSpriteScene,
+  place,
+  roundTrip,
+  runNode,
+  startWorld,
+} from '../helpers';
 
 /** A 100×100 wall at x = 200 and a 100×100 mover at the origin, both with box colliders, in a running world. */
 function wallAndMover() {
@@ -17,7 +27,12 @@ function wallAndMover() {
   f.stack.execute(new AddColliderCommand(f.sceneId, moverId));
   f.stack.execute(wallCollider);
   const { world, collisions } = startWorld(f, { collisions: true });
-  return { world, collisions, mover: world.findByObjectId(moverId)!, wall: world.findByObjectId(wallCollider.objectId)! };
+  return {
+    world,
+    collisions,
+    mover: world.findByObjectId(moverId)!,
+    wall: world.findByObjectId(wallCollider.objectId)!,
+  };
 }
 
 describe('the enabled switch', () => {