Nexo Mod 0.5.1-alpha

Adding a second Microsoft account no longer means signing out at
microsoft.com first.

Microsoft was silently reusing whatever session the browser already had, so
the sign-in button always came back with the same account. The authorize
request now asks for the account picker every time. It does not force a
fresh password prompt — an account you are already signed into is one click.

The launcher (Nexo Client 0.3.2) gets the identical change: both halves sign
into the same account store, so they had to agree.

Nothing else changed. Both editions are built from this commit.

Still true from 0.5.0: none of this has been tested in a running game,
and the chat history is stored unencrypted and unbounded.