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>

README.md

@@ -213,9 +213,10 @@ twice a second) in edit and play mode alike; `__gm.fps()` exposes the same numbe
 Rules that keep it organised: `core/` imports nothing from other layers; `ui/` never sees
 assets; position exists only on scene objects; overrides are merged in exactly one place
 (`core/properties/resolve.ts`); the inspector is generated from `PropertySchema` – a new
-property is one schema line; a new node is one file. Comments state contracts and reasons, not
-what the code does: a `/** */` on every export whose name does not say it all, `//` only for a
-decision or gotcha.
+property is one schema line; a new node is one file **plus a row in the table in
+`tests/core/node-catalog.test.ts`**, which fails if a node has no case. Comments state contracts
+and reasons, not what the code does: a `/** */` on every export whose name does not say it all,
+`//` only for a decision or gotcha.
 
 ## Development
 
@@ -226,11 +227,21 @@ npm install
 npm run dev          # http://localhost:5175/game-maker/dist/ – API calls are proxied to production
 npm test             # unit tests (core)
 npm run typecheck
+npm run lint         # ESLint, type-aware; --fix for the fixable half
+npm run format       # Prettier over src, tests and tools
+npm run check        # typecheck + lint + format:check + tests, what CI would run
 npm run build        # writes dist/ and regenerates index.html
 node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 140 editor checks, screenshots in /tmp/gm-e2e-*.png
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs   # the example game, played end to end
 ```
 
+**Prettier owns the formatting** (110 columns, single quotes, `.prettierrc.json`); Markdown is
+excluded because it pads table cells to equal width. ESLint therefore only ever means "this is a
+mistake", never "this looks different": `eslint-config-prettier` switches every stylistic rule
+off, and what is left is type-aware – unnecessary conditions, floating promises, duplicate
+imports, base-to-string. Where a rule fires on something deliberate, the disable comment states
+why (the `Log` node's `console.log`, a guard against untyped test hooks).
+
 Each script writes to its own project (`tools/lib/projects.mjs`): the **fixture** project is
 rewritten by every e2e run and the **jump-run** project by its seeder. The **playground**
 project is the author's own and is maintained in the editor – every tool refuses to touch it.