Set cmdTag as early as possible

Here's a claim that for a new command, cmdTag only gets set "after all the callins" https://discord.com/channels/549281623154229250/643197947441315840/1548386054044786738

Check if this is the case and see how early the tag assignment can be pushed. It can't be all the way back (because there's a handful of unsynced callins right at the start) but the earlier the identity of a command can be established via the tag the better.

Start by tracing where a new command is created and where cmdTag is assigned, then inspect the unsynced callins that occur at the start. Confirm how early the tag can be established without moving it before those callins. Done means cmdTag is assigned at the earliest safe point and existing command behavior remains unchanged.

Written by the indexing model from the issue text.