grammY Integration (Telegram Bot API)

Why grammY

TS-first Bot API client with built-in long-poll + webhook helpers, middleware, error handling, rate limiter.
Cleaner media helpers than hand-rolling fetch + FormData; supports all Bot API methods.
Extensible: proxy support via custom fetch, session middleware (optional), type-safe context.

Single client path: fetch-based implementation removed; grammY is now the sole Telegram client (send + gateway) with the grammY throttler enabled by default.
Gateway: monitorTelegramProvider builds a grammY Bot, wires mention/allowlist gating, media download via getFile/download, and delivers replies with sendMessage/sendPhoto/sendVideo/sendAudio/sendDocument. Supports long-poll or webhook via webhookCallback.
Proxy: optional telegram.proxy uses undici.ProxyAgent through grammY’s client.baseFetch.
Webhook support: webhook-set.ts wraps setWebhook/deleteWebhook; webhook.ts hosts the callback with health + graceful shutdown. Gateway enables webhook mode when telegram.webhookUrl is set (otherwise it long-polls).
Sessions: direct chats collapse into the agent main session (agent:<agentId>:<mainKey>); groups use agent:<agentId>:telegram:group:<chatId>; replies route back to the same provider.
Config knobs: telegram.botToken, telegram.dmPolicy, telegram.groups (allowlist + mention defaults), telegram.allowFrom, telegram.groupAllowFrom, telegram.groupPolicy, telegram.mediaMaxMb, telegram.proxy, telegram.webhookSecret, telegram.webhookUrl.
Draft streaming: optional telegram.streamMode uses sendMessageDraft in private topic chats (Bot API 9.3+). This is separate from provider block streaming.
Tests: grammy mocks cover DM + group mention gating and outbound send; more media/webhook fixtures still welcome.

Open questions

Optional grammY plugins (throttler) if we hit Bot API 429s.
Add more structured media tests (stickers, voice notes).
Make webhook listen port configurable (currently fixed to 8787 unless wired through the gateway).