test: verify published v0.2.0 artifact

[yigitcan-ozturk]

Post-release verification

• remove the one-time v0.2.0 publisher now that the release exists
• add a one-time post-release verifier
• download the published wheel from GitHub Release v0.2.0
• verify its SHA-256 digest against the published asset metadata
• clean-install it into a fresh virtual environment
• run rfqdiff --help
• run a representative CSV comparison using the released wheel
• validate recommendation, runner-up, margin, score breakdown, provenance and XLSX report output
• retain result/report evidence as an Actions artifact

No product or scoring behavior changes.