fix(regression): bad post actions alignment introduced in #3540

[SychO9]

Fixes a regression introduced in #3540

Changes proposed in this pull request:

• We can't reintroduce the clearfix, it messes with first post height (feat: use position: sticky for discussion side nav #3540).
• We don't want to un-hide Post-footer when it's empty (Hide post footer when empty #2926), but we can do so in normal posts only as it's the only reliable way atm. It doesn't pose a problem anyway unless extensions that add items leave those items hanging in the dom even if they're empty.

Screenshot

Necessity

• Has the problem that is being solved here been clearly explained?
• If applicable, have various options for solving this problem been considered?
• For core PRs, does this need to be in core, or could it be in an extension?
• Are we willing to maintain this for years / potentially forever?

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).
• Core developer confirmed locally this works as intended.
• Tests have been added, or are not appropriate here.

[davwheat]

Could we investigate the idea of using flex/grid instead of float for the stream/nav elements? This should let us reimplement the clearfix, while not affecting the height of the first post.

This (obviously implemented with a media query in core):

Plus removing the margin-right on the stream seems to do the trick.

We can then add back clearfix:

And then actions show correctly:

[SychO9]

@davwheat I'm worried it might easily break any existing custom styling, I think it would make more sense to do that in 2.0 when we refactor it all?

[davwheat]

I'm somewhat of the opinion that custom theming should be done with the new Less extenders we have to override files. In this case, as there are no DOM changes, there's no issue here.

Doing full rethemes without overriding the Less source results in even more CSS bloat than we currently have, which is an issue imo.

We've also done other Flex/Grid refactors in 1.x (Notifications List in 1.3, for example)