Here are some explorations about changes in process header and menu, in order to make the menu more visible and improve the phases indicator/CTA. Comments:

1. Hero style: we'd transition to a hero style, taking ideas from our initial proposal. The main reason is that this way we can have a more visible menu. Visually maybe its more appealling. We gain a little bit of vertical space. This hero version would allow to create different design footprints for different sections easily. For example for conferences we'd have a taller header without almost any other change.
2. Help system: I propose a system so that the user can close a help banner; if they do it, they will be able to open it again with a small widget in the same position. I think it'd work well as it's not intrusive at all and it fits with this new design.
3. New white phase box vs. new process intro blocks: if we decide to end up implementing the process intro blocks (System help / Process intro #4136) maybe they are a little bit similar/redundant with the new Phase Box in the header. I'd think first on the header, and if we like it, think about the Intro Blocks.
4. I've included a test when viewed in a super-wide screen. I think it'd work well.
5. This changes only affect the header, so implementation is clean.
6. I open a new issue to discuss what to do when items in the menu don't fit in a single line.

A. New header on process home

B. New header on proposals

C. New header with Intro Blocks

D. New header on super-wide screen

E. New header with short help

F. New header with long help

G. New header with help on proposals

Related with #4136 #3973

cc @decidim/product @decidim/lot-core