Admin impersonation: no reason field, in-place exit

Decision

Drop the free-text reason field from admin impersonation. On exit, mint a fresh admin custom token, sign back in with it, and route to /admin/users — no logout / re-auth round-trip.

Why

Free-text reasons were noise, not audit signal. The 30s TTL + user-facing email + admin_impersonations/{id} row remain the audit trail. Exit-as-logout forced re-auth between sessions.

Impact

• AdminStartImpersonationInputSchema drops reason.
• adminEndImpersonation mints a fresh admin custom token; the client calls signInWithCustomToken and routes back to /admin/users without signing out.
• Affects pillar-admin.

Status

Active.

Sources

• .context/wiki/decisions/* § "2026-05-30 — Admin impersonation: no reason field, in-place exit"