fix: resolve CI failures, linting issues, and refactor GSIFI validation
- Refactored \`scripts/validate_gsifi_governance_assets.py\` to handle JSON Schema validation and meet test expectations.
- Fixed Python linting (Black, Flake8, Pylint 10/10 score).
- Pruned irrelevant boilerplate GitHub Actions workflows.
- Added \`.github/labeler.yml\` with proper YAML header.
- Fixed line length issues in \`learnings.md\` for markdownlint.
- Verified all 37 repository tests pass locally.
Co-authored-by: OneFineStarstuff <87420139+OneFineStarstuff@users.noreply.github.com>