Swaps steps 3 and 4 in add-backlog.md so ROADMAP.md is updated before the phase directory is created. Directory existence is now a reliable indicator that a phase is already registered, preventing false duplicate detection in hooks that check for existing 999.x directories (Closes #2280). Also fixes renameDecimalPhases to preserve zero-padded directory prefixes (e.g. "06.3-slug" → "06.2-slug" instead of "6.2-slug"). Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>