fix(workspace): make file import a compact icon action

Place the import icon after New File and retain destination tooltips, accessible labels, and disabled state while importing.

Validation: WorkspaceFilesPanel tests passed (41 tests).

Release note: Replace the prominent file import button with a compact icon beside New File.

docs/features/assistant-workbar/workspace-files.md

@@ -6,7 +6,7 @@ FR-WF1：工作区展示当前项目执行目录内的实际文件。成果页
 已移除。旧布局只过滤 `results` 实例，保留其他实例、目标、展开状态和宽度；若活动实例被移除，
 按现有布局规则选择第一个保留实例。
 
-FR-WF2：文件页提供“导入文件”。初始目标为项目根目录；点击树中的目录后以该目录为目标，
+FR-WF2：文件页在“新建文件”后提供“导入文件”小图标按钮，悬停提示包含动作和目标目录，导入期间禁用并更新可访问名称。初始目标为项目根目录；点击树中的目录后以该目录为目标，
 点击文件后以其父目录为目标，“浏览此目录”同时更新目标。目标路径常显，打开选择器后固定
 本次项目与目标，不因切换会话或项目改变写入位置。本机从选定文件复制字节，远程上传到所选
 Host 的项目目录。支持二进制和空文件，不调用文档解析器，也不创建 artifact 数据库记录。

src/renderer/src/WorkspaceFilesPanel.tsx

@@ -600,9 +600,9 @@ export function WorkspaceFilesPanel({
         <button ref={refreshRef} className="icon-button" type="button" disabled={refreshing} aria-label={t('sidebar.workspace.refreshAriaLabel')} title={t('sidebar.workspace.refresh')} onClick={() => void refresh()}><RefreshCw size={14} aria-hidden="true" /></button>
       </div>
       {activeView === 'files' && root && <div className="workspace-files__toolbar workspace-files__actions">
-        <button className="secondary-button" type="button" disabled={importing} onClick={() => void importFiles()}><Upload size={14} aria-hidden="true" />{t(importing ? 'management.importing' : 'management.importFiles')}</button>
         <span className="workspace-files__destination" title={createTarget || '/'}>{t('management.importTarget', { path: createTarget || '/' })}</span>
         <button className="icon-button" type="button" aria-label={t('management.createFile')} title={`${t('management.createFile')}: ${createTarget || '/'}`} onClick={() => setDialog({ kind: 'createFile', path: createTarget })}><FilePlus size={14} aria-hidden="true" /></button>
+        <button className="icon-button" type="button" disabled={importing} aria-label={t(importing ? 'management.importing' : 'management.importFiles')} title={`${t(importing ? 'management.importing' : 'management.importFiles')}: ${createTarget || '/'}`} onClick={() => void importFiles()}><Upload size={14} aria-hidden="true" /></button>
         <button className="icon-button" type="button" aria-label={t('management.createDirectory')} title={`${t('management.createDirectory')}: ${createTarget || '/'}`} onClick={() => setDialog({ kind: 'createDirectory', path: createTarget })}><FolderPlus size={14} aria-hidden="true" /></button>
       </div>}
       {activeView === 'files' && browsedPath && <nav className="workspace-files__breadcrumbs" aria-label={t('management.path')}>