zq error presentation bugs

[philrz]

Repro is with Zui commit 445bdf1.

I spotted a couple bugs that seem related to when errors come back from zq in the Preview & Load screen. To easily trigger this I'm using the attached data-65536.txt which is a text file consisting of a single 64 KB string.

Two problems are shown in the attached video:

1. When I drag the file into Zui, Preview & Load shows the expected error message from zq because it's not in one of the formats supported by auto-detect. When it's still showing the long error from zq, the vertical scrollbar doesn't appear in Preview & Load area. I need to select a supported format like Line in order to get the vertical scrollbar to appear. Granted, there's not much sense in the user being able to enter pool config or see the Load button until zq has determined it's of a format that could survive load. However, at the end of the video you can see where I drag my /etc/passwd into the app and the vertical scrollbar appears despite the auto-detect failure, so it's currently inconsistent and the problem seems to be unique to when the error message from zq is huge. (zq could probably stand to truncate its error message in this case, but that's a separate topic.)

2. While studying that problem, I noticed that when it's showing the error message from zq there's no visible vertical line to make it obvious that the user can click & drag left/right to resize the Preview & Load area, but if I hover in just the right spot my mouse cursor changes and I can indeed resize. The vertical line appears as soon as I select a valid format. I don't know if subtle resize-ability areas without explicit lines are the hip trend in UX nowadays and I'm just slow to catch on [ 😄 ] but I figured I'd point it out just in case because seeing the vertical line appear & disappear looked funny to me.

Repro.mp4