Expose download smoke summary blockers at top level

[1613358894]

Summary

• repeat download-smoke summary blockers in the top-level blocking array for AI routing
• cover both bounded prepare and execute blocked outputs with focused tests
• document the top-level blocker behavior in the reference command contract

Why

AI controllers should not need to inspect nested command-specific summaries to identify why a download-smoke command is blocked. This keeps blocked states directly routable while preserving the detailed audit summaries.

Validation

• python -m pytest tests/test_cli_download_smoke.py -q --basetemp .pytest_tmp_top_level_blockers -p no:cacheprovider
• python -m pytest tests/test_docs_consistency.py tests/test_docs_hygiene_script.py -q --basetemp .pytest_tmp_top_level_blockers_docs -p no:cacheprovider
• python scripts/check_workspace_hygiene.py
• python scripts/check_docs_hygiene.py
• git diff --check
• bounded local missing-datasets probe: native exit 2, top-level blocking=[datasets_executable_missing], downloads_triggered=0, network_access=false, external_tools=false

Boundaries

No tool installation, provider lookup, broad download, external bioinformatics execution, tag, release, or asset upload was performed.