_keep_typing() was called with metadata= for thread-aware typing
indicators, but neither it nor the base send_typing() accepted
that parameter. Most adapter overrides (Slack, Discord, Telegram,
WhatsApp, HA) already accept metadata=None, but the base class
and Signal adapter did not.
- Add metadata=None to BasePlatformAdapter.send_typing()
- Add metadata=None to BasePlatformAdapter._keep_typing(), pass through
- Add metadata=None to SignalAdapter.send_typing()
Fixes TypeError in _process_message_background for Signal.
cea78c5e27