chore: rename skill and deduplicate feedback comments

[Wibias]

Summary

• rename the skill and release identity from shipping-github to github-delivery
• shorten every new agent-authored GitHub comment prefix to [GD]
• make Addressed feedback idempotent by PR head SHA instead of individual feedback ID
• aggregate all feedback resolved by the same head into one top-level comment
• retain backward-compatible parsing for earlier long-form resolution records

Addressed-feedback format

[GD] Addressed feedback

feedbacks:
- issue_comment:123
- review_comment:456

commit: abc1234

<!-- gd:addressed-feedback head:<40-char-head-sha> -->

Before publishing, the agent searches for the exact head marker. It edits that comment when present instead of posting one comment per feedback item.

Validation

• regression test reproduced the prior duplicate-comment behavior before the fix
• focused addressed-feedback tests pass after the fix
• full npm run check passed on the implemented tree
• final CI reruns on Linux, macOS, and Windows with Node.js 20 and 22
• Dependency Review and CodeQL run on the final head

Commit structure

1. atomic skill rename plus feedback-comment behavior and tests
2. protected release-workflow artifact rename