fix: use actual passing design count on job dashboard

[amandazhuyilan]

Pull Request

Summary

SBP-658: use actual passing design count on job dashboard, not requested count

Changes

• Added extract_rfdiffusion_design_count(): counts rows in ranked_designs.csv (the same file the max score is already read from).
• Added an optional extract_design_count hook on WorkflowResultsSpec, wired only into the bindcraft/rfdiffusion (de-novo-design) specs — every other workflow keeps final_design_count as None, unchanged.
• ensure_completed_run_score() now also computes this count when a run completes and overwrites RunMetric.final_design_count with it, alongside the existing max-score caching. B
• Added 6 new tests

How to Test

CI tests shall pass!

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have added or updated documentation where necessary
• I have run linting and unit tests locally
• The code follows the project's style guidelines