Add a platform-aware route target system so a single route can forward
to several destinations at once (e.g. a Discord channel and a Telegram
group). Route.target becomes Route.targets[] with per-entry platform,
channelId/threadId for Discord and chatId/topicId for Telegram; the
legacy single-target format is normalized on load and accepted by the
admin API.
Implement the Telegram driver with HTML rendering and Bot API
sendMessage (chat_id + message_thread_id for topics, retry on 429/5xx),
plus /gh commands served over POST /telegram/webhook: login, logout,
comment, merge and close. The comment/merge/close commands resolve the
issue or PR from the replied-to notification message. OAuth binding now
stores a D1 telegram_links mapping and replies with a confirmation.
Sync the Telegram webhook from the scheduled trigger via setWebhook.
Skip re-processing when the same X-GitHub-Delivery id is seen (KV, 300s TTL)
to stop double pushes when both an org and an App webhook target the worker.
Pass ExecutionContext through so dispatch runs via waitUntil instead of a
fire-and-forget that gets frozen. Cache the imported HMAC key per secret.
