gh-1157: Add CosmologyWithInverseComovingDistance protocol

[paddyroddy]

Description

Adds a CosmologyWithInverseComovingDistance protocol as inv_comoving_distance isn't used that often.

Closes: #1157

Changelog entry

Added: A CosmologyWithInverseComovingDistance protocol

Checks

• Is your code passing linting?
• Is your code passing tests?
• Have you added additional tests (if required)?
• Have you modified/extended the documentation (if required)?
• Have you added a one-liner changelog entry above (if required)?

[Copilot]

Pull request overview

This PR refactors the typing surface around cosmology capabilities by introducing a dedicated CosmologyWithInverseComovingDistance protocol, so consumers can require inv_comoving_distance only where it’s actually needed.

Changes:

• Remove HasInverseComovingDistance from the base Cosmology protocol and introduce CosmologyWithInverseComovingDistance.
• Update glass.shells.distance_grid to require the new protocol.
• Update test type annotations to reference the new protocol (with one inconsistency noted in review comments).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
glass/cosmology.py	Splits inverse-comoving-distance capability into a dedicated protocol.
glass/shells.py	Tightens distance_grid’s cosmology type requirement to the new protocol and updates its parameter docs.
tests/core/test_shells.py	Adjusts test typing imports/annotations to align with the new protocol (needs a small follow-up for consistency).

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[connoraird]

I'm surised there were no changes needed in the tests but what do I know

[paddyroddy]

I'm surised there were no changes needed in the tests but what do I know

So I had previously modified the tests, but reverted these changes due to a Copilot review. inv_comoving_distance is only called in distance_grid and hence it only needs CosmologyWithInverseComovingDistance. test_distance_grid calls distance_grid, but the test itself would "work" with Cosmology only. This was the comment #1164 (comment).

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.