[3.0] Puts the forum title and logo back in a band of their own

[albertlast]

Description

Reverts the layout half of #9373. Confirmed with live627 as the direction to take on #9423: the merged header is not what people expect of this theme, whatever the theme branch does.

Back to:

#top_section   user links, language picker, search      full width, banded
#header        forum title, logo                        width-limited, transparent
#main_menu     the menu                                 full width band

Measured on the board index at 1280px after the change:

	x	width	height
#top_section	0	1281	35
#header	64	1153	67
#main_menu	0	1281	25

which is the layout in the "expected result" screenshot on #9423. Checked at 1280px and at 480px, where the search box and the logo drop out as they did before.

Two commits, deliberately separate:

1. The revert itself, which is git revert 6fa05ff1f with the conflicts resolved to keep everything that landed after it.
2. Tokens for the top bar. The revert restores the rule as it was before the top bar was ever tokenised — wave 2 covered base, buttons, frames, boxes, quotes and overlays, and the top bar was in none of those groups, so [3.0] Theme split (wave 3, part 5) — Move the top bar into the header as a user panel #9373 deleted it before it ever got its own. Literal colours in index.css are the wrong direction for a file where #main_menu right under it already reads from --mainmenu-*, so it gets --topsection-* to match.

Values are unchanged by the second commit. The band's background came from the shared gradient rule near the end of the file, not the #fff in its own rule, so the token holds that gradient and the selector list loses its entry; the border is identical to the menu band's. Computed values before and after:

	before	after
background-image	linear-gradient(rgb(226,233,243) 0%, rgb(255,255,255) 70%)	same
border-bottom	0.571429px solid rgb(187,187,187)	same
box-shadow	rgba(0,0,0,0.16) 0px 1px 4px 0px	same
background-color	rgb(255,255,255)	rgba(0,0,0,0)

The last row is the /* fallback for some browsers */ colour behind an opaque gradient, which #main_menu also dropped when it was tokenised.

What is not reverted: #9374 and #9375 stay exactly as they are, so the menu is still a band across the page and the footer is still a flex row. The <header> landmark from #9371 stays too — only the class moves back onto it.

Other consequences:

• The --header-* tokens and the .user_panel rule existed only for the merged header and go with it. The header sets no background, border or shadow any more, so tokens for those would describe nothing. Nothing else references either; checked across Themes/.
• The Go up link points at #top_section again, since that is the first thing on the page once more.
• MaintenanceTemplate.php and the ExportProfileData.php XSLT follow the forum's header, so the wrapper class goes back onto the header element in both. That reverts [3.0] Gives the other two copies of the header the same wrapper #9426, which was correct only while the header had an inner wrapper.

#9425 is superseded by this and closed — it centred the title and logo in a row that no longer exists.

Issues References (Fixes|Related|Closes)

Fixes #9423
Related #7933