Prepare verifier adoption loop release

[pengfei-threemoonslab]

Summary

Prepare the v0.11.0 verifier adoption loop release surfaces around the verify-first workflow.

• Updates public discovery/docs surfaces to lead with verify --preview, verifier artifacts, merge_verdict, fix_task, and pinned v0.11.0 snippets.
• Adds the verify-native ai_generated_refund_pr fixture that writes verifier.json, report.json, and pr-comment.md for the blocked refund PR demo.
• Adds provisional agents-shipgate feedback export for redacted design-partner feedback artifacts, with docs/feedback-schema.v0.1.json and .well-known schema/output metadata.
• Adds explicit GitHub Action rollout policies for blocking only merge_verdict == blocked and requiring can_merge_without_human == true.
• Updates stability contracts, agent-skill/adoption-kit content, changelog, and tests for the new verifier and feedback surfaces.

Validation

• python -m ruff check .
• python -m pytest (2399 passed, 4 skipped)
• PYTHONPATH=src:. python -m agents_shipgate contract --json
• PYTHONPATH=src:. python -m agents_shipgate verify --preview --json --out /tmp/shipgate-preview-final
• PYTHONPATH=src:. python -m agents_shipgate fixture run ai_generated_refund_pr --out /tmp/shipgate-refund-pr-final
• PYTHONPATH=src:. python -m agents_shipgate feedback export --from /tmp/shipgate-refund-pr-final/verifier.json --redact --out /tmp/shipgate-feedback-redact-check.json --json

Notes

This prepares the repository release surfaces. Publishing GitHub/PyPI releases and updating the live website/CMS remain release-ops steps outside this local workspace.