fn sign_in_channel(channel: Option<&str>) -> Option<&str>Expand description
The channel whose own MuxBus sign-in this process uses. A channel is the
unit of sign-in, not the host: every channel but stable (the installed
releases, which have always used the host-wide set) signs in on its own, so
two channels on one machine can be signed in at once, to the same account
or to different ones, and one’s refresh, sign-in or sign-out never touches
the other’s (SPEC_MUXBUS_SIGN_IN_PER_CHANNEL_2026_10_08.md).