v1.7.0

Added

• GET /client/text-chat-tools (ai_agents:read), the tools a text agent
  may call in a chat, starting with handoff_to_human.
• The text_chat_conversations:write scope and its two routes, which turn the
  AI on or off for one text conversation: PUT /client/chat-conversations/{uuid}
  and PUT /client/text-chats/{provider_type}/channels/{channel_identifier}/conversations/{provider_conversation_id}.
• references/text-chat-handoff.md: what handoff_to_human does, the four
  questions to settle with a client before binding it, how the bot switch
  behaves, and why dashboard test chats cannot show a handoff.
• references/voice-handoff.md: the cold and warm transfer tools compared,
  what only Ingfah's team can configure (numbers, ring timeout, hold and
  no-answer messages), the questions to settle with a client, and how to
  verify a transfer from the call's messages.

Fixed

• The revision guard now checks a text agent's text_chat_tools. Before, a
  prompt-only revision that omitted them silently unbound handoff_to_human.