dsh-phoenix: Seamless Restart and Goal Continuity in DeepSeek Harness

Native restarts in DeepSeek Harness (dsh) interrupt tasks. dsh-phoenix enables seamless task continuation across restarts through persistent checkpoints, safe restart mechanisms, and automatic client reconnection. It marks the resume target using the `pendingResume` flag and refreshes pages via a heartbeat script, forming a complete autonomous evolution loop that resolves disconnection and data loss issues during plugin updates.