Two new seams on the composer, both through the existing contribution
registry: a data area whose providers resolve badge descriptors per
session, and a render area for a chrome-free strip below the surface.
Core registers nothing in either — they stay empty until something
contributes.
Providers resolve from live session context rather than registering
static entries, so a contribution can be conditional without the
reactive when() the registry deliberately doesn't offer.
Brooklyn Nicholson
1cefad5523