Fix red develop 6e8fe9921790

The merge lane found `develop` red at `6e8fe9921790008b8be0e597eafe4c3bbcc8eeab` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `tests/test_host_platform_guard.py::test_no_host_specific_spelling_outside_the_seam_beyond_the_frozen_residual` - `jaahd-unit-pytest` The whole gate log: artifact `8083` on lane task 8845. 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 6e8fe9921: raised runner_cli_pins.py fcntl residual 4→6 in the host_platform guard (8810's agy host lock; module runs `python3 -I`, can't import the seam). Quick gate green; PR #6575 queued to the merge lane. Memory: none applied.