Renamed check_warnings to check_for_warnings for consistency

[VisLab]

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[github-actions]

PR Review: Rename check_warnings → check_for_warnings

Verdict: LGTM

This is a clean, minimal rename for consistency with the rest of the codebase (e.g., ErrorHandler, check_compliance, BIDS tools, CLI all use check_for_warnings).

Checked:

• No remaining uses of the old check_warnings keyword argument anywhere in the repo.
• validate_schema and validate_schema_object are internal script utilities, not exported from hed/__init__.py, so there is no public API breakage.
• The only external callers (validate_schemas.py, hed_convert_schema.py) call validate_all_schemas, which in turn calls validate_schema with no keyword argument, so the rename has no impact there.
• All test methods and docstrings updated consistently.
• The added inline comment (# Ensure errors are listed before warnings) correctly explains the issues = errors + warnings reassignment.

No issues found.