Pull DVC data from subprojects

[lntutor]

Summary

• delegate DVC pulling to Calkit’s recursive pull command
• avoid modifying Git state with --no-git
• add an action-contract test to prevent regression

Validation

• python3 scripts/test-action.py
• git diff --check

Resolves calkit/calkit#1042

[rebeccamccabe]

Tested this out in the following CI run:
https://github.com/symbiotic-engineering/MDOcean/actions/runs/30932629568
and it seems like calkit pull --no-git also doesn't recursively pull subprojects. I would expect to see a bunch of added files in mdocean/simulation/modules/OpenFLASH/pubs/JFM/figs from the subproject.