Replace PR body generating claude command with a skill

[nstrayer]

Summary

Replaces the older .claude/commands/draft-pr-body.md command with a new positron-pr-helper Claude Code skill that provides a richer, more interactive workflow for creating PR bodies.

Key improvements:

• Dynamic test tag fetching: Always pulls the latest e2e test tags from test-tags.ts instead of relying on a static, manually-maintained list
• Interactive workflow: Guided question-and-answer flow to gather PR context (issue number, type, summary, screenshots)
• Better categorization: Automatically categorizes test tags by type (feature, platform, performance, special)
• Multiple output options: Copy to clipboard, update existing PR via gh, save to file, or display
• Comprehensive templates: Separate templates for bug fixes, new features, UI changes, and maintenance PRs
• Helper script: Includes fetch-test-tags.sh for standalone tag extraction

This command writing this PR body:

Release Notes

New Features

• N/A

Bug Fixes

• N/A

QA Notes

This is a development tooling improvement. To test:

1. Invoke the skill: Please use the positron-pr-helper skill
2. Answer the interactive questions about your PR
3. Verify the generated PR body includes:
   • Proper formatting (Summary, Release Notes, QA Notes sections)
   • Current e2e test tags from test-tags.ts
   • Appropriate template based on PR type
4. Test one of the output options (clipboard, file, or gh pr edit)

The skill should handle various PR types: bug fixes, new features, UI changes, and maintenance work.

[github-actions]

E2E Tests 🚀
This PR will run tests tagged with: @:critical

^{readme  valid tags}

[seeM]

LGTM, one minor change