Fix risk of accepting packets before firmware is loaded

[typenoob]

This PR fixes an error that occurs when a remote device repeatedly sends HCI_CONNECTION_REQUEST_COMMAND early while the local device still needs to load its firmware driver:

[2026-06-29 09:01:39.812] WARNING in host: HCI_ACCEPT_CONNECTION_REQUEST_COMMAND failed (UNKNOWN_CONNECTION_IDENTIFIER_ERROR)
Task exception was never retrieved
future: <Task finished name='Task-5' coro=<Host.send_async_command() done, defined at C:\Users\user\nxbt\.venv\Lib\site-packages\bumble\host.py:805> exception=HCI_Error()>
Traceback (most recent call last):
  File "C:\Users\user\nxbt\.venv\Lib\site-packages\bumble\host.py", line 829, in send_async_command
    raise hci.HCI_Error(status)
bumble.hci.HCI_Error: HCI_Error(hci/UNKNOWN_CONNECTION_IDENTIFIER_ERROR [0x2])

The root cause is that Host.ready was incorrectly set to True before the firmware driver had finished loading successfully.

In addition, I believe letting Drivers control Host.ready is risky, so this behavior has been consolidated and moved into Host.reset instead.

[typenoob]

I believe you can reproduce this issue on Windows by first putting the remote device into pairing mode, and then calling the Intel Bluetooth adapter's Device.power_on function.

[typenoob]

Testing, linting, and formatting were not performed yet.