Add justfile and update package.json scripts

CLAUDE.md

@@ -9,7 +9,7 @@ see `docs/plans/2026-02-23-single-combat-plan.md` for implementation plan.
 
 ## tech
 
-- bun (serve + test), biome (lint/format, 4 spaces)
+- bun (serve + test), biome (lint/format, 2 spaces)
 - vanilla js, es modules, no framework, no build step
 - html/css rendering (no canvas)
 - client-only for now, multiplayer later

justfile

@@ -0,0 +1,13 @@
+default:
+    @just --list
+
+lint:
+    bun run lint
+
+typecheck:
+    bun run typecheck
+
+test:
+    bun run test
+
+check: lint typecheck test

package.json

@@ -2,7 +2,10 @@
   "name": "slaywithfriends",
   "private": true,
   "scripts": {
-    "check": "bunx biome check --write && bun test",
+    "lint": "bunx biome check --write .",
+    "typecheck": "bunx tsc --noEmit",
+    "test": "bun test",
+    "check": "bun run lint && bun run typecheck && bun run test",
     "dev": "bun run src/serve.js"
   },
   "devDependencies": {