test: add CLI failure path tests for check_wheel_contract (#152)

[Som0111]

Description

Fixes #152

Type of change

• 🐛 Bug fix (non-breaking change which fixes an issue)

🛡️ Sovereign Developer Checklist

• I picked task test(packaging): cover invalid wheel archives and CLI failure output #152 from the good first issues list
• I have added tests for my changes
• I have executed make all locally (uv/make not available in my environment; ran python -m pytest tests/test_check_wheel_contract.py -q directly → 7 passed)
• I updated CHANGELOG.md (test-only change, no user-visible behavior change)

🤖 AI assistance and data handling

• I used AI assistance (Claude Code) to help write the tests; I reviewed the complete diff and take responsibility for the submitted work
• I did not upload private vault data, credentials, tokens, or unpublished security details
• I reviewed the complete diff

🧭 Contract impact

• This PR does not affect any documented contract — test-only change, no production code touched

Screenshots / CLI Output

python -m pytest tests/test_check_wheel_contract.py -q
7 passed (4 pre-existing + 3 new)

3 new tests added:

• test_cli_reports_missing_wheel_path
• test_cli_reports_malformed_archive_without_raising
• test_cli_accepts_valid_wheel