Navigation look without navigation module

Problem/Motivation

We are targeting Drupal 11.3 minimum where:

• Gin 6 will become the admin theme
• Navigation will be out of experimental and (I guess) activated by default

In the same time, this is issue is stalled because of the incompatibility between Navigation and Admin toolbar 📌 [1.0.0-beta1] Evaluate Navigation module's top bar API Active

However, there is something "safe" we can take from this other issue: the cleaner look.

Proposed resolution

Tasks:

• Adopt toolbar/gin font
• Remove background stripes
• Toolbar height: from 72px to 64px
• Clean form layout
• Harmonize spacing

Bug fixes:

• Toolbar button alignment
• Form details icon position
• Shoelace menu items are HTML checkboxes. Some themes (like taiwlind) are styling checkboxes a bit aggressively.
• Drawer title overflow
• Hide the weird form API artefact

Out of scope:

• change z-index, absolute positioning. Jean did a lot effort to make them compatible with toolbar, admin toolbar, navigation...
• Other branding compliance: colors, icons, button shape... let's do it after beta1, taking the time