test(tenancy): await split-host projections (#157)

[smiggleworth]

Change

Give the administrator-access and staff-membership projection polls their own 45-second windows after the corresponding invitation acceptance succeeds. The earlier invitation-token poll consumed part of the shared deadline, so the later polls could skip directly to an assertion after otherwise successful acceptance.

Poll the tenant projection until it reports active after the administrator team becomes readable. The team and tenant projections are independent; their visibility can arrive in either order.

Evidence

• PR #371 CI run 35916466821 failed at the administrator-access assertion (Forbidden instead of OK).
• PR #370 CI run 35917447426 observed provisioning immediately after the team became readable.
• Focused split-host broker tests for both affected cases: 1/1 each passed after the changes.
• Targeted dotnet format and git diff --check: passed.
• Current-head CI run 35919416926: Validate, dependency review, and native AMD64/ARM64 checks passed on 1155859b1ec1c5c6e3fab77ee4a7efd31afc6805.

This changes only test polling. Keep #157 open for the remaining tenancy proof.