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/core/graph/NodeContext.ts

@@ -22,12 +22,20 @@ export interface EntityHandle {
 
 /** World position of a handle: its local position plus those of all ancestors. */
 export function worldPositionOf(handle: EntityHandle): { x: number; y: number; z: number } {
-  return sumAlongChain(handle, (h) => h.parent, (h) => h);
+  return sumAlongChain(
+    handle,
+    (h) => h.parent,
+    (h) => h,
+  );
 }
 
 /** Whether a handle and every ancestor of it are switched on (see `properties/enabled.ts`). */
 export function isHandleEnabled(handle: EntityHandle): boolean {
-  return enabledAlongChain(handle, (h) => h.props, (h) => h.parent);
+  return enabledAlongChain(
+    handle,
+    (h) => h.props,
+    (h) => h.parent,
+  );
 }
 
 /** Where the mouse is (world units) and what it did this frame. */
@@ -83,7 +91,11 @@ export interface NodeContext {
    * local to `parent` (world when none). Returns null when the asset does not exist or cannot
    * be placed (a scene). Spawned behaviors run their `On start` on the next tick.
    */
-  spawn(assetId: string, position: { x: number; y: number; z: number }, parent: EntityHandle | null): EntityHandle | null;
+  spawn(
+    assetId: string,
+    position: { x: number; y: number; z: number },
+    parent: EntityHandle | null,
+  ): EntityHandle | null;
   destroy(target: EntityHandle): void;
   stop(): void;
   /** Ends the run and starts it again from the saved scene (everything spawned is lost). */