Fix red develop 3c056a31993f

The merge lane found `develop` red at `3c056a31993fb0c6f1d82f6892d895bdc1a52067` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `tests/test_git_access.py::test_no_cookie_authenticated_get_mutates_state` - `api-unit-dc-test` The whole gate log: artifact `14389` on lane task 12716. Make `develop` pass its full gate again. Open a PR as usual: the merge lane merges a PR that fixes some of these and adds no failure even while `develop` is red.

Fixed red develop: the Lax GET scan now exempts GET /api/org/setup's server-derived onboarding latch, pinned to its exact writes (test-only). Quick gate + changed-area tests green; PR #7748 queued in merge lane. Memory: none applied.