Add multi-connection Live panel with 1-4 parallel connections

Replace singleton serial/logcat/SSH handlers with a connection registry
supporting up to 4 concurrent live connections. Each connection gets a
compact card with minimap, stop/restart/save/remove controls, and live
line preview. Unified IPC channels carry connectionId for routing.

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

Author: ozgesolidkey