feat(ops): add signal freshness SLOs

[oktofeesh1]

Summary

Adds signal freshness SLO reporting so stale, blocked, or missing signal sources are visible before public-review readiness is considered healthy.

What changed

• Added a freshness SLO report covering registry data, scoring model snapshots, GitHub totals, repo sync segments, decision packs, bounty data, and signal snapshots.
• Exposed freshnessSlo on readiness, sync status, and stale decision-pack refresh responses.
• Added a signals.freshness_slo audit event with redacted count/status/affected-area metadata.
• Added OpenAPI schema coverage plus unit and integration tests for fresh, stale, missing, blocked, malformed timestamp, API, and queue audit paths.

Why

Issue #40 needs freshness SLOs and alertable audit events so stale signal data cannot silently pass readiness checks.

Validation

• npm run test:ci
• npx vitest run test/unit/data-quality.test.ts test/unit/queue.test.ts test/integration/api.test.ts test/unit/openapi.test.ts
• Codex Security diff scan: no findings

Notes

Closes #40

[JSONbored]

PR #54 — request changes
feat(ops): add signal freshness SLOs

Required changes:

• Do not make readyForPublicReview depend on optional/missing freshness signals unless they are truly launch-blocking.
• Avoid deriving global freshness from only the latest 200 signal snapshots; this can hide stale/missing per-repo/per-contributor data as the project grows.
• Connect SLO breaches to repair/alert behavior, not only readiness reporting.
• Add tests for optional bounty/decision-pack absence, large snapshot sets, stale per-repo signals beyond the recent sample window, and repair queue behavior.

issues resolved