Update Changelog

Append phase tracking or final summary to thoughts/NNNN-description/changelog.md.

When to Use

During Implementation (after each phase):

• Document what was actually done vs planned
• Note deviations and reasons
• List files changed
• Capture discoveries

At Completion (after all phases):

• Append FINAL SUMMARY section
• Summarize key deviations
• Document lessons learned
• Note technical debt and follow-up work

Phase Update Format