Add support for Discord commands that were previously returning
"not supported":
- ListSessions / SessionDeleter: read and delete pi session .jsonl
files, enabling /list and /delete commands
- HistoryProvider: read conversation history from pi session files,
enabling /history command
- ReasoningEffortSwitcher: map to pi's --thinking flag with levels
off/minimal/low/medium/high/xhigh, enabling /reasoning command
- SkillProvider: expose .pi/skills/ directories, enabling /skills
- GetWorkDir: expose work directory for /status display
Session file discovery uses pi's path encoding convention where
absolute paths are encoded as --path-segments-- directory names
under ~/.pi/agent/sessions/.
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
