feat(workspace): add cpu core status display and safer quick command actions

Expose `cpuCores` in backend status collection with multi-command fallback
and surface it in the status panel as a localized CPU core badge under the
CPU model.

Adjust terminal group UX by adding a server-level close-all control in the
SSH tab group header.

Reduce accidental quick command execution by switching list interaction to
single-click select + double-click execute, while preserving keyboard Enter
and context-menu execution paths.

.helloagents/archive/2026-04/202604120656_server-status-cpu-core-display/.status.json

@@ -0,0 +1 @@
+{"status":"completed","completed":4,"failed":0,"pending":0,"total":4,"done":4,"percent":100,"current":"Completed - server status CPU core display implemented and verified","updated_at":"2026-04-12 07:01:00"}