Add installation tests for direct dependents (BioC-style)

In Bioconductor, packages are tested against first-order dependents. We should consider doing this, as done for `scverse` packages depending on `AnnData`: https://github.com/scverse/integration-testing/actions/runs/18115461787.

In this way we can flag installation incompatibilities early, and have an incentive to move to slimmer requirements over time.