Automate live-QA as e2e via the Telegram test DC

[miridius]

Manual live-QA (driving the dev bot via web.telegram.org) is the only coverage for several user-visible flows; automate it as e2e against Telegram's test DC.

Requirements:

• Test-DC bot + the local telegram-bot-api server in test mode + an MTProto userbot that sends messages, taps confirm/cancel buttons, edits, and asserts on the bot's replies.
• Also owns the container-level shutdown e2e (the manual QA script from 2026-07-05): SIGTERM a prod-style one-off mid-download (expect abort, job row kept) and mid-send (expect drain, exactly one delivery).
• Do after the plugin extraction (Extract workflow skills/gate scripts/agents into a claude-plugins marketplace repo #19).