feat: add PR template heuristics command

[huntharo]

Summary

• add a JSON CLI command to find PRs that still contain the PR template verbatim or nearly verbatim
• support local template files or auto-discovery from common GitHub PR template paths
• add section-aware distance scoring for the copied template block from ## Summary through ## Risks and Mitigations
• report both section-level and full-body edit distances for triage

Testing

• pnpm --filter @ghcrawl/api-contract test
• pnpm --filter @ghcrawl/api-core test
• pnpm --filter ghcrawl test
• pnpm typecheck

[github-actions]

Cluster Performance

• Status: PASS
• Fixture median: 479.8 ms (12 samples, 3 cluster rebuilds/sample)
• Fixture baseline: 535.1 ms
• Fixture delta: -55.3 ms (-10.3%)
• Projected openclaw/openclaw duration: 8m 58.0s
• Projected openclaw/openclaw baseline: 10m 0.0s
• Projected delta: -61994.8 ms (-10.3%)
• Regression threshold: +50.0%
• Fixture shape: 512 threads x 3 source kinds
• Sample durations: 496.8 ms, 487.5 ms, 482.9 ms, 486.8 ms, 465.6 ms, 479.1 ms, 480.6 ms, 465.4 ms, 478.8 ms, 469.1 ms, 469.3 ms, 486.4 ms

Run: workflow run for 9470dce