Move to the shared CCPBioSim workflows release 0.9.0 #473

Problem or motivation

CodeEntropy is pinned to release 0.4.0 of the shared CCPBioSim workflows, and the open Renovate PR (#464) only moves it to 0.6.0. Release 0.9.0 removes the ci-lowest-dependencies workflow, which two of our jobs call, so a plain pin bump would fail. We also still override docs, pre-commit and coverage to Python 3.15, although the package declares support for 3.12 to 3.14.

Proposed solution

1. Move every shared workflow pin to 0.9.0, as the full commit SHA with a # 0.9.0 comment.
2. Replace the two ci-lowest-dependencies calls (the lowest-dependencies job in pr.yaml and dependency-floors.yaml) with ci-test-python and lowest-dependencies: true. Keep test-path: tests/unit and the OS list.
3. Use the shared defaults for docs, pre-commit and coverage Python instead of the 3.15 overrides. If 3.15 support is intended, add the classifier and the matrix entry deliberately in this change.
4. Leave the regression jobs, system discovery and multi-OS lists as they are.
5. Close the Renovate PR (chore(deps): update ccpbiosim/.github action to v0.7.0 #464) in favour of this change.
6. If job names change, update the required status checks in branch protection.

Additional context

Release 0.9.0 changes: the conda test workflow is simplified, the lowest-dependencies check is a flag on the Python test workflow, runners default to ubuntu-26.04, zizmor ignores are inline, the website payload sends repo and tag, and Renovate updates pre-commit hooks. The local regression workflows also hard-code Python 3.15. That is out of scope here.