Re-examine (and align) issuable headers

Issue

The header is slightly different across issuables:

** Note: Work items will all share the same Vue app on the FE, which will naturally result in consistency. See [INITIATIVE] Work Items (&6033) for more context.

Proposal

Take inventory of all current issuables and see how they currently align or differ. We can then decide how to proceed-

  • Should the headers all follow the same basic structure? Should we document that in Figma the same way we did for MR widgets?
  • Should they all have the issuable layout, or could some be detached (for example, do they all need the sidebar?)

Brought up in: Update issue top header UI to match merge requests (!85586 - closed)

From @gweaver

  • MR title isn't sticky (i wish it was), but issues is (which i like)
  • MR state + author info is below title, on issues it is above title (see below)
  • When sticky header is active, it has to use a different component in order to get the status to show to the left of the title because on issues, the status is above the title and not on the same line.
  • Sticky header doesn't have the control buttons (edit, actions sub-menu), so you have to scroll all the way to the top in order to interact with them.

From @uhlexsis

  • Edit is now exposed after clicking and when editing rather than being replaced with the edit form itself (eg the pencil button is replaced with the editing form currently). I am not 💯 what users would expect here- maybe the button disabling, maybe the button changing to some kind of save/publish cta, maybe being hidden as it is now, maybe just having it still exposed and clickable is fine, etc. Most of these could be difficult to implement without reorganizing the content a bit.
  • There is no longer a tooltip explaining that Edit will impact only the title and description. If we wanted to be super clear we would label the button itself explaining what it is editing, but that is a looong title.
  • The proximity of the button is also now not as close to what it is editing, but tbf editing the title & description is editing the issue. The proximity of the current pencil button could also lead the user to believe they are editing only the title. I could make the assumption that this proposed edit will make this action easier to find even if it may not return totally the expected behavior (edit full page vs just title vs title description etc) - which could be interesting to test out and/or get feedback on.

cc @uhlexsis @nickleonard @pedroms @phikai @beckalippert @ameliabauerly

Edited by Gabe Weaver