[Feature Request / PR-Ready] Add explicit "Delete Session" action with danger styling to session menu (ui-workspace)

[codeREDxbt]

Summary / 概述

Currently, the session action menu (...) in the sidebar only provides:

• 重命名 / Rename
• 分叉会话 / Fork session
• 归档会话 / Archive session (with an archive folder icon)

As noted in packages/client/ui-workspace/README.md ("No Session deletion or unarchive control"), users who want to delete conversations cannot find an explicit "Delete" button. This leads to confusion and perceived clutter.

Proposed Solution / 解决方案

1. Add a dedicated "Delete session" / "删除会话" action to SessionNodeItem with red danger styling (danger: true) and <IconTrashOutline16 />.
2. Map it to the underlying archiveSession method so the session is cleanly removed from the sidebar tree and search results without corrupting append-only event persistence logs.

Code Changes / 变更代码

• packages/client/ui-workspace/src/client/locales.ts:

  // zh
  'delete.session': '删除会话',
  // en
  'delete.session': 'Delete session',

• packages/client/ui-workspace/src/client/rows/Rows.tsx:

  const sessionMenuItems = [
    { id: 'rename', label: t('rename'), icon: <IconEditOutline16 /> },
    { id: 'fork', label: t('menu.fork'), icon: <IconBranchOutline16 /> },
    { id: 'archive', label: t('menu.archiveSession'), icon: <IconArchiveOutline20 size={16} /> },
    { id: 'delete', label: t('delete.session'), icon: <IconTrashOutline16 />, danger: true },
  ]

• packages/client/ui-workspace/src/client/rows/WorkspaceBrowser.tsx:
  Passed onSessionDelete={onSessionArchive} across both grouped (SessionTree) and flat (FlatList) browser views.

Verification / 测试结果

• All 161 tests in packages/client/ui-workspace passing.
• Verified danger styling and dispatch in rows.client.spec.tsx and workspace-browser.client.spec.tsx.