feat(nav): Lock secondary nav to always be expanded on settings pages

[JonasBa]

Settings pages have structured navigation that users need to browse — collapsing the sidebar here creates a worse experience because it removes the primary way to move between settings sections.

When a user is on any settings route, the secondary sidebar is now always visible regardless of their collapsed preference. The collapse toggle button is hidden, and the Ctrl+B/Cmd+B keyboard shortcut has no effect while on settings routes. When the user navigates away from settings, their previous collapsed/expanded preference is restored.

Implemented by passing the active route group as a prop from PrimaryNavigationContextProvider down to SecondaryNavigationContextProvider, where it overrides the view to 'expanded' and makes setView a no-op when the group is 'settings'. The header component reads activeGroup from usePrimaryNavigation() to conditionally hide the toggle button.

[getsantry]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you remove the label Waiting for: Community, I will leave it alone ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀