Server side (session_router.py):
- /reconnect now accepts sessions in "active" state (not just "disconnected")
- When client reconnects to an active session, the old WebSocket/pipeline is
automatically replaced when the new WebSocket connects
- Only truly terminal states (e.g. "ended") return 409
Flutter side (agent_call_page.dart):
- Distinguish terminal errors (404 session gone, 409 ended) from transient
errors (network timeout, server unreachable) in reconnect loop
- Terminal errors break immediately instead of wasting retry attempts
- Extract _connectWebSocket() helper for cleaner reconnect flow
- Add DioException handling for proper HTTP status code inspection
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>