fix(tvix/cli): add toplevel docstring to Args struct r/8481

Otherwise the flattened `ServiceUrlsMemory` docstring becomes the main
binary description, which doesn't make an awful lot of sense.

The help now describes what this CLI does currently (an interface to use
the different Tvix component.

Also, describe what it does not, so people running it without looking
too much other documentation might not get confused about why this
doesn't do anything in `/nix/store`, or doesn't provide the same CLI
surface as Nix.

Change-Id: Ia4838b444f03a10821801a6171d3e956b3cdfdaf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12194
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

0 files changed, 0 insertions, 0 deletions