Add non-blocking CI check to detect API breaking changes

[LalatenduMohanty]

Problem

PR #1129 renamed the WorkContext.__init__ parameter constraints_file to constraints_files and changed it from a required positional argument to a keyword-only argument with a default. This was an API-incompatible change that broke downstream consumers (specifically the AIPCC wheels builder).

The commit message documented the breaking change in the body, but it was easy to miss during review — there was no automated signal to flag it.

Proposal

Add a non-blocking CI job that automatically detects public API signature changes on pull requests using griffe. This would cover:

• Renamed or removed function/method parameters
• Changed parameter types or defaults
• Removed functions, classes, or modules
• Changed class __init__ signatures

The check would:

• Run only on pull requests
• Compare the PR branch's API against origin/main
• Use continue-on-error: true so it does not block merging — it serves as a warning system
• Not be added to Mergify merge conditions

This gives PR authors and reviewers visibility into breaking changes without adding friction to the development process.

Implementation sketch

1. Add a scripts/check_api_changes.py script using griffe to diff the API
2. Add an api-check hatch environment with griffe as a dependency
3. Add a non-blocking job to .github/workflows/check.yaml