Ecosystem: registry / marketplace partnership integration

[MarouaBoud]

Summary

Make the MCP Quality Score consumable by registries and marketplaces so a server's
grade travels with its listing. Builds on the existing scoring API (mcp-quality serve):
harden it into a partner-facing integration with verifiable, re-checkable scores.

What it builds [net]

• Verifiable scores — every score carries rubric_version + provenance_hash so a
  registry can re-verify a badge wasn't hand-edited (anti-gaming, already in the report).
• Batch scoring — score a list of servers (registry ingest) with stable JSON per the
  versioned mcp-quality/report@1 schema.
• Partner docs + examples — a reference integration (webhook / CI action) a registry can
  drop in to grade submissions and surface the badge.
• Freshness — a re-score cadence / staleness marker so listed grades don't drift from
  the current surface.

Acceptance criteria

• serve exposes batch scoring + a documented verify endpoint returning provenance.
• A worked example integration (CI action or webhook) in docs/.
• Scores are reproducible and provenance-verifiable across releases (rubric_version).
• No secrets required for public-surface scoring; auth headers supported for private servers.