Drop the standalone OIDC_AUTH_DEFAULT_TENANT_MODE / oidc_auth.default_tenant_mode
knob so OIDC auto-provisioning and local password registration share the single
auth.default_tenant_mode policy (resolved by the callback handler). Repair
tenantless sessions by falling back to the first active membership on the login
happy path and stale-preference paths, allow tenantless PUT /auth/me/preferences,
clear the tenant snapshot on /auth/me responses without a tenant, and default the
frontend canCreateTenant capability to fail-closed until /auth/me confirms it.
wizardchen
87ba3fc2de