Resolve the caller's control-plane principal, memberships, and Buzz lifecycle state

SIWX, a control-plane session, or a scoped grant key bearer authenticates the caller and returns the resolved principal, active org memberships, and independent Buzz adoption/installation/enrollment eligibility and drift. A wallet and a Buzz proof are authenticators or attribution evidence, never owners by themselves. A grant key resolves to its own subject principal (typically with no memberships of its own, since a grant key acts via a project_grant rather than membership) — resolving your own identity actuates and leaks nothing beyond it, so this is grant-key-capable the same way the cold-restart-recovery POST /projects/v1/:project_id/tokens is.