feat(telegram): add configurable regex wake-word gating for group text and media

[mcleay]

What does this PR do?

This PR adds Telegram-specific group invocation gating with configurable regex wake words.

The goal is to let Hermes ignore ambient group chatter while still responding to explicit Telegram group triggers. It adds Hermes-side gating for Telegram group messages and captions so the bot only responds when explicitly invoked.

Changes Made

• Added Telegram config bridging in gateway/config.py for:
  • telegram.require_mention
  • telegram.mention_patterns
• Added Telegram group invocation handling in gateway/platforms/telegram.py
• Group messages are now processed when they:
  • match a configured regex wake word
  • reply to one of the bot’s messages
• Strips the matched wake-word prefix from the beginning of the text/caption before dispatching to the model
• Applies the same invocation gating to media/caption messages, not just plain text
• Avoids mutating Telegram Message objects directly when cleaning invocation prefixes
• Added focused Telegram gating tests in:
  • tests/gateway/test_telegram_group_gating.py

Example config

telegram:
  require_mention: true
  mention_patterns:
    - "^\\s*wakeword\\b"

With the example above:

• wakeword hi in a group is processed
• a plain uninvoked group message is ignored
• an image with caption wakeword what is this is processed
• a plain image with no caption is ignored
• replies to the bot are processed

How to Test

Run:

• pytest -q tests/gateway/test_telegram_group_gating.py tests/gateway/test_telegram_text_batching.py

Then verify in a Telegram group where the bot receives group messages:

• plain text with no invocation is ignored
• wakeword hi is processed
• reply-to-bot is processed
• plain image with no caption is ignored
• image with a wake-word caption is processed

Notes

• This is Telegram-specific behavior and does not change Discord or other platform adapters.
• The tests use generic placeholder names/patterns rather than user-specific wake words.

Checklist

• Code changes tested
• Group text invocation gating works
• Group media invocation gating works
• No private/local config included
• No user-specific bot names or wake words used in tests