Fix Issue 6347: default constraints not applying to other categories

[matteius]

Fix issue with default constraints not applying to other categories + tests.

The issue

Fixes #6347

The checklist

• Associated issue
• A news fragment in the news/ directory to describe this fix with the extension .bugfix.rst, .feature.rst, .behavior.rst, .doc.rst. .vendor.rst. or .trivial.rst (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.

[Copilot]

Pull Request Overview

This PR fixes issue #6347 by ensuring that default package constraints are always applied when installing dev packages. Key changes include:

• Updating the resolver to always add and use default constraints for dev packages.
• Adding integration tests in tests/integration/test_dev_package_constraints.py to verify that the default constraints are correctly enforced.
• Modifying constraint resolution logic in pipenv/utils/resolver.py to include locked versions from default packages for dev packages.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tests/integration/test_dev_package_constraints.py	Adds integration tests validating the proper enforcement of default constraints on dev packages.
pipenv/utils/resolver.py	Updates constraint logic to always apply default constraints for dev packages and propagate default package locked versions.

Comments suppressed due to low confidence (1)

pipenv/utils/resolver.py:921

• [nitpick] Consider replacing this direct console print with a logging mechanism (or gating it behind a verbosity flag) to avoid unintended debug output in production environments.

st.console.print(f"Adding constraint: {pkg_name}{version}")