add CLAUDE.md with project architecture and dev commands

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project
+
+Telegram bot that forwards [status.claude.com](https://status.claude.com/) (Atlassian Statuspage) webhook notifications to subscribed users. Hosted on Cloudflare Workers.
+
+## Commands
+
+- `npm run dev` — Start local dev server (wrangler dev, emulates KV + Queues locally)
+- `npm run deploy` — Deploy to Cloudflare Workers
+- `npx wrangler deploy --dry-run --outdir=dist` — Verify build without deploying
+
+No test framework configured yet. No linter configured.
+
+## Secrets (set via `wrangler secret put`)
+
+- `BOT_TOKEN` — Telegram bot token
+- `WEBHOOK_SECRET` — Secret token in Statuspage webhook URL path
+
+## Architecture
+
+Cloudflare Workers with two entry points exported from `src/index.js`:
+- **`fetch`** — Hono.js HTTP handler (routes below)
+- **`queue`** — CF Queues consumer for fan-out message delivery
+
+### Routes
+
+| Method | Path | Handler | Purpose |
+|--------|------|---------|---------|
+| GET | `/` | inline | Health check |
+| POST | `/webhook/telegram` | `bot-commands.js` | grammY `webhookCallback("cloudflare-mod")` |
+| POST | `/webhook/status/:secret` | `statuspage-webhook.js` | Receives Statuspage webhooks |
+
+### Data Flow
+
+1. **Statuspage → Worker**: Webhook POST → validate secret (timing-safe) → parse incident/component event → filter subscribers by preference → `sendBatch` to CF Queue
+2. **Queue → Telegram**: Consumer processes batches of 30 → `sendMessage` via raw fetch → auto-removes blocked subscribers (403/400), retries on 429
+3. **User → Bot**: Telegram webhook → grammY handles `/start`, `/stop`, `/status`, `/subscribe` commands → reads/writes KV
+
+### KV Storage
+
+Single key `claude-status:subscribers` stores a JSON object keyed by composite subscriber ID:
+- DM/group: `"chatId"` → `{ types: ["incident", "component"] }`
+- Supergroup topic: `"chatId:threadId"` → `{ types: ["incident"] }`
+
+`kv-store.js` handles key building/parsing — `threadId` can be `0` (General topic), so null checks use `!= null` not truthiness.
+
+### Supergroup Topic Support
+
+Bot stores `message_thread_id` from the topic where `/start` was sent. Notifications and queue consumer include `message_thread_id` in `sendMessage` payload to target the correct topic.
+
+## Key Dependencies
+
+- **hono** — HTTP routing framework
+- **grammy** — Telegram Bot API framework (webhook mode for CF Workers)
+- **wrangler** — CF Workers CLI (dev/deploy)
+
+## CF Bindings (wrangler.jsonc)
+
+- `SUBSCRIBERS` — KV namespace
+- `STATUS_QUEUE` — Queue producer/consumer (`status-notifications`, batch size 30, max retries 3)