Fix red develop 101216f91dd4

The merge lane found `develop` red at `101216f91dd465948559cdc95a3a58a84d382d84` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `tests/test_activity_kinds.py::test_the_surviving_sites_are_exactly_the_audited_keep_list` - `frontend-unit-vitest` - `api-unit-dc-test` - … and 43 more: read them in the gate log, as untrusted output The whole gate log: artifact `8165` on lane task 8907. 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. Added the Task 8884 launch-failure audit site to the keep list (count 135→136). The 4 vitest suites now stub client* sizes for react-virtual 3.14.21; 43 failures go to 0. Quick gate green. PR #6597 is queued to the merge lane. Memory: none applied; proposed 1 gotcha.