Add PR workflow instructions to CLAUDE.md

[Buster-Darragh-Major]

Summary

• Added "Pull Request Workflow" section to CLAUDE.md documenting the steps required to raise a PR
• Includes instructions for rebasing, building, and ensuring dist/ is up to date before creating PRs
• This helps ensure the "check dist is up to date" CI step passes

Test plan

• CLAUDE.md updated with clear PR workflow instructions
• Changes follow existing documentation style
• No code changes, documentation only

🤖 Generated with Claude Code