Session Manager

@djimontyp/task-tracker-session-manager

Manages work sessions with pause/resume workflow. Triggers on "покажи сесії", "show sessions", "список сесій", "list sessions", "що далі", "what's next", "які плани", "what are the plans", "що по планам", "які цілі", "what are the goals", "що робимо", "what should we do", "де ми", "where are we", "продовжити", "continue", "resume", "давай", "let's go", "пауза", "pause", "зупинись", "stop", "статус", "status", "що зроблено", "what's done", "прогрес", "progress", "перемкнутись", "switch", "заархівувати", "archive". Replaces NEXT_SESSION_TODO.md with structured session files in planned/active/paused/completed dirs. Auto-saves progress, bilingual EN/UA.