feat(channel): use Telegram rich and ephemeral messages when supported

## Background

The Telegram channel in #2271 currently targets `python-telegram-bot>=22.8`, whose supported Bot API does not expose the newer rich-message and ephemeral-message capabilities discussed during review.

## Follow-up

When python-telegram-bot supports the required Bot API versions:

- use `sendRichMessage` for native table rendering instead of ASCII tables inside `

`

- use ephemeral messages for group approval prompts so only the requester can see and act on them

- retain safe fallbacks for Telegram clients or deployments where these APIs are unavailable

- add compatibility and permission tests for both paths


Follow-up from #2271.

Start with the Telegram channel work in #2271 and verify when python-telegram-bot supports the required Bot API versions and rich or ephemeral message APIs. Done means native table rendering and requester-only approval prompts use those APIs when available, safe fallbacks remain, and compatibility and permission tests cover both paths.

Rédigé par le modèle d'indexation à partir du texte de l'issue.