Fix autofix failure resolution + reduce reusable Python CI setup time

[stranske]

Why\n\nAutofix sometimes fails to detect lint/format failures for the workflow run that triggered it (especially when PR head advances), and reusable Python CI setup time is inflated by implicit heavyweight dependency installs.\n\n## Scope\n\n- Improve autofix failure detection and rate-limit resilience.\n- Reduce Python 3.11/3.12 CI runtime by removing implicit heavyweight dependency installs from the reusable workflow.\n\n## Non-Goals\n\n- Changing repo-specific dependency management policies beyond the reusable workflow defaults.\n- Adding new workflows or new consumer features.\n\n## Tasks\n\n- [ ] Update autofix workflow to resolve failures against triggering run SHA and proceed on PR-file-list rate limits\n- [ ] Mirror autofix changes into consumer templates\n- [ ] Remove implicit heavyweight baseline installs from reusable Python CI\n- [ ] Ensure workflow YAML validation passes\n\n## Acceptance Criteria\n\n- [ ] Autofix runs reliably identify lint/format failures from the triggering run SHA\n- [ ] Autofix does not skip entirely when PR file listing hits a GitHub API rate limit\n- [ ] Reusable Python CI no longer installs heavyweight baseline dependencies implicitly\n- [ ] Workflows validate via scripts/validate_workflow_yaml.py and repo CI passes\n\n## Implementation Notes\n\nFiles:\n- .github/workflows/autofix.yml\n- templates/consumer-repo/.github/workflows/autofix.yml\n- .github/workflows/reusable-10-ci-python.yml\n\nBranch: fix/event-hub-reusable-workflows\nPR: #1502\n