Accept canonical GitHub repository casing

[chubes4]

Summary

• compare authorized GitHub owner/repository identity case-insensitively during post-publication verification
• retain strict HTTPS pull URL shape, pull number, exact API html_url, and target repository checks
• cover canonical mixed-case acceptance and different-repository rejection

Fixes #1874.

How to test

1. Run npm ci.
2. Run npm run test:native-agent-task-lifecycle.
3. Run npm run test:runner-workspace-publisher.
4. Run git diff --check origin/main...HEAD.
5. Confirm the lifecycle fixture accepts request target automattic/build-with-wordpress with canonical publication/API identity Automattic/build-with-wordpress.
6. Confirm a publication for other/repo remains rejected.

All commands pass locally.

Compatibility

No extension-path or backwards-compatibility impact. GitHub repository identity is case-insensitive; URL syntax, pull identity, target binding, and API verification remain strict.

Source evidence

• https://github.com/Automattic/build-with-wordpress/actions/runs/29663992711
• Correct developer workflow provenance documentation build-with-wordpress#121

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode with OpenAI GPT-5.6 Sol
• Used for: Diagnosed the post-publication casing mismatch, implemented fail-closed identity normalization, added regression coverage, and ran verification. Chris reviewed and owns the change.