Covers what the coach interfaces promise before anything builds on them: goal and habit ownership and limits, one check-in per habit, goal and day dated in the user's time zone, streaks across weekends and weeks, and a rhythm that keeps exactly one main-bot routine per check-in and is idempotent when set again. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MRtGG9ARfqqhma3t85Ro2u