better formatting for zed unknown sub-command error message

[mccanne]

We should improve the DX of the zed command error message when encountering an unknown command, e.g.,

$ zed lo
"zed": no such sub-command "lo": options are: auth branch create delete drop index init load log ls merge query rename revert serve use vacate dev

The prefix "zed" should not be in quotes but the sub-command should be.

And the options should be vertically separated with horizontal tab.