pi session context persistence, fix new session button, add clear all sessions

- handle pi process death by nulling piProcess ref so next message respawns
- replay conversation history on respawn via --session flag
- fix user message JSONL format to array for pi compatibility
- fix container sessions mount to match storage path
- fix ChatPanelWrapper: key on inner component so usePiChat resets on new session
- add bulk delete sessions endpoint and clear all button in chat header

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/servers/api/terminal/websocket.ts

@@ -194,7 +194,7 @@ const startDockerSidecar = async (port: number, homeDir: string, userId: number,
       '-v', `${getUserToolsDir(email)}:/officer/user/tools:ro`,
       '-v', `${PI_CONFIG_DIR}:/officer/pi-config:ro`,
       '-v', `${PI_CONFIG_DIR}:${containerHome}/.pi/agent`,
-      '-v', `${ensureDir(join(DATA_PATH, email, 'pi-sessions'))}:${containerHome}/.pi/agent/sessions`,
+      '-v', `${ensureDir(join(getHomeDir(email), '.pi', 'agent', 'sessions'))}:${containerHome}/.pi/agent/sessions`,
       '-v', `${join(DATA_PATH, '.generated')}:/officer/generated:ro`,
       ...googleMounts,
       '-v', `${join(DATA_PATH, email, 'integrations')}:/officer/user/integrations:ro`,