fix: remove tool notification rate limit

[QueryPlanner]

What

Remove rate limiting from Telegram tool notifications so each parallel tool call gets its own notification.

Why

The previous implementation used a 100ms rate limit window for tool notifications. When the agent made 3 parallel log_meal calls within 7ms, only the first notification was sent. This was confusing because the user only saw one notification but the agent reported calling the tool 3 times.

How

• Removed rate limiting logic from notify_telegram_before_tool() in src/blacki/callbacks.py
• Removed unused _TOOL_NOTIFY_* state variables
• Kept rate limiting for notify_telegram_after_model() (intermediate LLM text) since streaming could still spam
• Updated test test_notify_rate_limits_per_chat → test_notify_sends_for_each_tool_call

Tests

• All 828 tests pass
• Ruff format/check pass
• Mypy type check passes
• 100% test coverage maintained

[gemini-code-assist]

Code Review

This pull request removes the rate-limiting logic for Telegram tool notifications, ensuring that a notification is sent for every tool call. The changes include the removal of rate-limiting state variables and the associated logic within the notification function, along with updates to the test suite to reflect the new behavior. I have no feedback to provide as there were no review comments.