Add operational-value graders for EU CRA workflows

[Copilot]

Adds measurable operational outcomes for the EU CRA workflow suite, aligned with each worker’s specification goals.

• Repository assessment workers

  • Register schema-v4 graders for all six CRA assessment workers.
  • Bind evidence to a frozen target commit.
  • Count value only after explicit acceptance by a non-bot reviewer.

• Package maintainer

  • Measure the share of assigned ledger gaps resolved through human-reviewed changes.
  • Preserve stable opportunity keys and replayable evidence.

• Workflow contract

  • Add machine-readable evidence markers and human-acceptance guidance:

<!-- operational-value: domain=scope-classification target=OWNER/REPO target-sha=40_HEX_SHA -->

• Coverage and documentation
  • Extend workflow contract coverage for all seven graders.
  • Document direct-checkout support and the existing package-transport limitation.