Fix personalization tab wrap and workspace/group-chat picker UX

[XYAIStudio]

Summary

Dashboard UX polish on latest main. Three related layout/interaction fixes, no Release assets, no merge.

1. Personalization top nav wrap — path tabs use flex-wrap instead of a single-row Ant Segmented that clipped labels. Title/subtitle stay horizontal (writing-mode: horizontal-tb + min-width) so CJK no longer stacks top-to-bottom when the window is narrow.
2. Chat expert/agent picker multi-select — checkboxes are additive; row click still inserts a 1:1 @ mention. 进入群聊 creates or reopens a group with the host + checked set (WeChat-style + @ prefill).
3. Projects/Tasks/Chats zone — removed the tall lavender 新建对话 / 新建任务 / 新建项目 / 建群 stack from the left sidebar. The workspace page now has three large horizontal tabs (对话 | 任务 | 项目) above the live list. 建群 stays a primary action on the 对话 tab.

Target branch

• Base is develop (feature / fix — default)
• Base is main (requested: branch from latest main)

Type of change

• Bug fix
• New feature

Before / after

Personalization

• Before: seven tabs forced onto one row and clipped; title/description rendered as a one-character-wide vertical column.
• After: tabs wrap onto extra rows with readable spacing and a clear active pill; title and subtitle read left-to-right.

Personalization tabs wrap on a narrow window

Workspace zone

• Before: four full-width create buttons stacked in the left rail.
• After: 对话 | 任务 | 项目 tabs sit above the list; matching 新建 action lives with the active tab; 建群 is the primary action on 对话.

Workspace conversation tab with New conversation and New group

Chat picker

• Before: picking an expert only toggled one @ mention and closed the popover.
• After: check several experts/agents, then 进入群聊; single-click still does the existing 1:1 mention.

Test plan

• make all passes locally (dashboard-only change; focused Vitest + tsc --noEmit green)
• Added/updated tests (PageShell, ExpertPickerPopover, groupChats, openGroupChat)
• Browser: logged in as admin, narrowed Personalization to 780px — tabs wrap, title stays horizontal, switching tabs still works
• Browser: /projects shows 对话/任务/项目 tabs; 建群 is primary on 对话; 任务/项目 host their own 新建 actions; left rail no longer stacks the four create buttons

cd dashboard && npx vitest run \
  src/layouts/PageShell.test.tsx \
  src/pages/Chat/components/ExpertPickerPopover.test.tsx \
  src/utils/groupChats.test.ts \
  src/utils/openGroupChat.test.ts \
  src/pages/Chat/components/ChatInputActionsRow.test.tsx
cd dashboard && npx tsc --noEmit

Windows / narrow window: shrink Personalization and confirm tabs wrap instead of clipping.

Checklist

• Updated CHANGELOG.md (if user-facing)
• README / docs updated (if needed)

Do not merge. Do not upload Release assets.

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