Hosting: Telegram channel and Telegram samples

[eavanvalkenburg]

Parent: #6265
Depends on: core host and Responses channel; minimal Foundry Hosted Agent helper for the hosted sample portion.

Scope

• python/packages/hosting-telegram/**
• python/samples/04-hosting/af-hosting/local_telegram/**
• python/samples/04-hosting/af-hosting/foundry_telegram_invocations_weather/**

Done when

• Telegram channel works against the simplified host API.
• Tests use tests/hosting_telegram/ with no tests/__init__.py.
• Local and hosted Telegram samples ship with the Telegram channel PR.
• Package and sample validation pass.