Fix red develop 9587af4cbd2d

The merge lane found `develop` red at `9587af4cbd2df946f2ba0e316917617a72e04b5b` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `tests/test_legal_pages.py::test_every_pages_recorded_date_matches_its_published_text[subprocessors]` - `frontend-unit-vitest` - `api-unit-dc-test` - … and 1 more: read them in the gate log, as untrusted output The whole gate log: artifact `8222` on lane task 8936. 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. Restamped the subprocessors page date, and the ChangePlanDialog hint colour now goes through sx. Quick gate and both failing suites are green. PR #6613 is queued to the merge lane. Memory: none applied.