[fix.dirac.ρ.D9+] Workspace routing must not replace the scientific workbench

Rebuilding exposed a product-shell regression: connected 3D Views inherited the full Workspace chrome and a forced Mid-century molecular palette, so an architecture layer visually replaced the established Dirac tool.

Keep full navigation on scaffold pages, restore the native scene workbench and Light/Dark controls, default molecular colouring to Graphite, and expose Workspaces as one deliberate entry instead.

Author: ivanicu