Changelog

Generate or update CHANGELOG.md in any project by gathering new changes from plan files, git commits, or merged GitHub PRs and rewriting them into a clean, audience-appropriate changelog. Auto-detects existing changelog style (user-facing "What's New" vs. Keep a Changelog) and the best available source. Use whenever the user asks to update the changelog, generate release notes, summarize recent work for users, write a "What's New" or "What shipped this week", or refresh CHANGELOG.md after merges — even if they don't explicitly say "changelog". Do NOT use for ad-hoc commit-message writing, single-PR descriptions, or producing internal standup reports (use `progress-report`…