Add run_constrained support to grayskull dependency updates

[ctcjab]

Description:

The update-grayskull inspection feature now updates run_constrained dependencies when bumping package versions. This prevents stale version constraints that can break downstream packages.

Changes:

• Add "run_constrained" to SECTIONS_TO_PARSE
• Add new SECTIONS_TO_UPDATE_CONSTRAINTS_ONLY constant for conservative updates
• Add constraints_only parameter to _apply_env_dep_comparison()
• Update _apply_dep_update_v1() and apply_dep_update() to handle run_constrained
• Update generate_dep_hint() to show run_constrained updates

The constraints-only behavior for run_constrained:

• ✅ Updates version constraints for packages in both recipe and grayskull
• ❌ Does NOT add new packages (optional deps are maintainer's choice)
• ❌ Does NOT remove packages (maintainer may have specific reasons)

This conservative approach fixes stale constraints while respecting maintainer decisions about which optional dependencies to include.

Checklist:

• Pydantic model updated or no update needed

Cross-refs, links to issues, etc:

Fixes #5645

Real-world example: litellm-feedstock had stale uvicorn constraint >=0.31.1,<0.32.0 instead of upstream's >=0.32.1,<1.0.0, breaking packages like notebook_intelligence.

[beckermr]

This PR needs testing against v1 recipes. Those recipes put run constraints in a different part of the recipe.

[ctcjab]

@beckermr thanks for the quick review! Since I am not sure when I'll have time to pick this back up, anyone reading this please feel free to take over here. Happy to grant anyone permission to push to my branch as needed.

[beckermr]

OK. happy to wait on this PR until you have time.

[ctcjab]

This PR needs testing against v1 recipes. Those recipes put run constraints in a different part of the recipe.

Added a test for a v1 recipe in ce05015.

But based on https://conda.org/learn/ceps/cep-0014/#requirements-section and https://docs.conda.io/projects/conda-build/en/latest/resources/define-metadata.html#run-constrained both v1 and v0 recipes use the same location, requirements.run_constrained. Let me know if I'm missing something, and thanks again for the quick review.

[beckermr]

It is called for v0 (conda-build)

requirements:
  run_constrained:
    - optional-subpackage =={{ version }}

and for v1 (rattler-build)

requirements:
  run_constraints:
    - optional-subpackage =={{ version }}

See https://github.com/prefix-dev/recipe-format/blob/c33fce275c3d721a892abf95ef1c43bd6f96012c/examples/valid/single-output/recipe.yaml#L115

Notice it is run_constrained vs run_constraints.

[ctcjab]

Oops, thanks for catching that! Fixed in 034de92:

• Updated _apply_dep_update_v1() to look for run_constraints in v1 recipes
• Updated the test to use the correct v1 section name

The internal dep_comparison dict still uses run_constrained as the key for consistency, but when applying to v1 recipes the code now correctly maps it to run_constraints.