Feed update unintenionally marks currently selected article as read

[plata]

Setup:

• show all articles by default (not highlights)
• update on start

Behavior:

• the currently selected (first) article is opened
• new articles are added to the list, this looks a bit messy because there's a lot of visible changes in the list
• selected article position in the list is not focused anymore and the article is marked as read

Possible solutions:

• do not select and open article automatically, i.e. wait until it selected manually
• show loading overlay during update such that interaction with list is not possible
• insert new articles at the top of the list but keep currently visible list entries where they are, i.e. new entries would be hidden above (this is what e.g. Feeder does)

[cscarney]

I think that this is a regression in the transition to Qt6. The original (and intended) behavior was:

1. the first article doesn't automatically open while an update is in progress. An "Update in Progress" placeholder is displayed in the article pane.
2. Articles can still be manually selected and opened during an update.
3. When the update is complete, the first article in the list is opened, unless the user has already selected one manually.