feat: scaffold plug-n-play telegram bot on cloudflare workers

grammY-based bot with a module plugin system loaded from the MODULES env
var. Three command visibility levels (public/protected/private) share a
unified command namespace with conflict detection at registry build.

- 4 initial modules (util, wordle, loldle, misc); util fully implemented,
  others are stubs proving the plugin system end-to-end
- util: /info (chat/thread/sender ids) + /help (pure renderer over the
  registry, HTML parse mode, escapes user-influenced strings)
- KVStore interface with CFKVStore and a per-module prefixing factory;
  getJSON/putJSON convenience helpers; other backends drop in via one file
- Webhook at POST /webhook with secret-token validation via grammY's
  webhookCallback; no admin HTTP surface
- Post-deploy register script (npm run deploy = wrangler deploy && node
  --env-file=.env.deploy scripts/register.js) for setWebhook and
  setMyCommands; --dry-run flag for preview
- 56 vitest unit tests across 7 suites covering registry, db wrapper,
  dispatcher, help renderer, validators, and HTML escaper
- biome for lint + format; phased implementation plan under plans/

vitest.config.js

@@ -0,0 +1,15 @@
+import { defineConfig } from "vitest/config";
+
+// Pure-logic tests only. No workerd pool — we stub KV and bot in-memory.
+export default defineConfig({
+  test: {
+    environment: "node",
+    include: ["tests/**/*.test.js"],
+    passWithNoTests: true,
+    coverage: {
+      provider: "v8",
+      reporter: ["text", "html"],
+      include: ["src/**/*.js"],
+    },
+  },
+});