fix(ui): refine command line and clipboard

- preserve command history colors after reopening
- remove collapsed command bar residue and split the unsaved prompt
- read system text when the drawing clipboard is empty

Refs #467
Refs #468
Refs #470

locales/zh-CN/opencadstudio.ftl

@@ -89,6 +89,11 @@ modal-unable-save = 无法保存图形
 modal-drawing-changed = 磁盘上的图形已更改
 modal-delete-layer = 删除图层
 modal-unsaved-changes = 未保存的更改
+modal-unsaved-save-prompt = 是否要保存更改？
+clipboard-no-supported-content = 剪贴板中没有受支持的文本或图形对象。
+clipboard-unavailable = 系统剪贴板不可用。
+clipboard-occupied = 系统剪贴板当前正被使用，请重试。
+clipboard-conversion-failed = 无法读取剪贴板文本。
 modal-point-style = 点样式
 modal-attribute-editor = 属性编辑器
 modal-save-drawing-as = 图纸另存为