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>

package.json

@@ -9,11 +9,22 @@
     "build": "tsc --noEmit && vite build",
     "preview": "vite preview",
     "test": "vitest run",
-    "typecheck": "tsc --noEmit"
+    "typecheck": "tsc --noEmit",
+    "lint": "eslint .",
+    "lint:fix": "eslint . --fix",
+    "format": "prettier --write .",
+    "format:check": "prettier --check .",
+    "check": "npm run typecheck && npm run lint && npm run format:check && npm run test"
   },
   "devDependencies": {
+    "@eslint/js": "^10.0.1",
     "@types/node": "^22.20.1",
+    "eslint": "^10.10.0",
+    "eslint-config-prettier": "^10.1.8",
+    "globals": "^17.12.0",
+    "prettier": "^3.9.6",
     "typescript": "^5.6.0",
+    "typescript-eslint": "^8.70.0",
     "vite": "^6.0.0",
     "vitest": "^3.0.0"
   },