polish(web): 打磨 Web 会话界面的布局、自适应与组件一致性

1. 统一会话列宽度轴：新增 --dsh-chat-content-width（748px），输入框、todo、goal、queue、approval、plan review、ask question 等容器的宽度与边距全部由该变量推导，消除各面板之间的像素漂移，窄视口下的边缘留白也保持一致。
2. 输入框自适应与细节：控制行改为容器查询（460px 阈值以下权限选择器只显示图标+下拉，隐藏文字）；卡片圆角 20→22、行内边距调整并整体下移 2px（发送按钮除外）；permission/model 触发器统一 24px 圆角；Plan 与 Read Only 间距 +8。
3. 修复浮层菜单溢出：slash 菜单与命令弹层钳制到输入卡片宽度，超长行以省略号截断；Tooltip 增加 12px 视口边缘安全距离。
4. 增加与替换图标：Add provider 改用输入框同款加号图标（IconPlusOutline16），统一图标尺寸与字号。
5. 统一 Settings → Models 组件：补齐按钮 hover 态、select 下拉箭头不再贴边、标题区与 provider 卡片间距 +12。
6. 侧边栏交互：add workspace / group by / create session / 收起侧边栏四个图标按钮增加 500ms 延迟 tooltip（前两个向下弹出）；展开态的 New Session 不再重复显示 tooltip；侧边栏窄屏自适应收起逻辑微调。
7. 其他：hero 区 workspace 徽章右移对齐；附带 Agent Note（中英双语）记录共享宽度轴与容器查询的设计取舍。

packages/client/ui-models/tests/components.spec.tsx

@@ -155,7 +155,7 @@ describe('ModelsSection', () => {
     expect(screen.getByText('openai')).toBeTruthy()
     expect(screen.queryByText('Active')).toBeNull()
     expect(screen.queryByText('Inactive')).toBeNull()
-    expect(screen.getByText(`+ ${en.add}`)).toBeTruthy()
+    expect(screen.getByText(en.add)).toBeTruthy()
   })
 
   it('turns the setup card into a row once the credential reports configured', async () => {
@@ -332,7 +332,7 @@ describe('ModelsSection', () => {
 
   it('adds a dormant provider with a derived reference and stores its key', async () => {
     const { mutate, set } = await mountSection()
-    fireEvent.click(screen.getByText(`+ ${en.add}`))
+    fireEvent.click(screen.getByText(en.add))
     const pick = await screen.findByLabelText<HTMLSelectElement>(en.provider)
     expect([...pick.options].map(option => option.value)).toEqual(['anthropic', 'broken', 'plain'])
     expect(pick.value).toBe('anthropic')
@@ -356,7 +356,7 @@ describe('ModelsSection', () => {
 
   it('switches the add card target and degrades unknown or broken targets loudly', async () => {
     await mountSection()
-    fireEvent.click(screen.getByText(`+ ${en.add}`))
+    fireEvent.click(screen.getByText(en.add))
     const pick = await screen.findByLabelText<HTMLSelectElement>(en.provider)
     fireEvent.change(pick, { target: { value: 'broken' } })
     await screen.findByText(/unresolvable settings path/)
@@ -374,7 +374,7 @@ describe('ModelsSection', () => {
     const { set } = await mountSection({
       mutate: vi.fn(() => Promise.resolve(fail('llm-pi-ai: unknown pi-ai provider "bogus"'))),
     })
-    fireEvent.click(screen.getByText(`+ ${en.add}`))
+    fireEvent.click(screen.getByText(en.add))
     await screen.findByLabelText(en.provider)
     const keys = screen.getAllByLabelText<HTMLInputElement>(en.keyInput)
     fireEvent.change(keys[keys.length - 1] as HTMLInputElement, { target: { value: 'sk-x' } })
@@ -554,7 +554,7 @@ describe('ModelsSection', () => {
     />)
     expect(screen.getByText(en.readOnly)).toBeTruthy()
     expect(screen.getAllByText<HTMLButtonElement>(en.remove).every(button => button.disabled)).toBe(true)
-    expect(screen.getByText<HTMLButtonElement>(`+ ${en.add}`).disabled).toBe(true)
+    expect(screen.getByText<HTMLButtonElement>(en.add).disabled).toBe(true)
   })
 
   it('toggles the row editor closed on a second edit click and on cancel', async () => {
@@ -573,10 +573,10 @@ describe('ModelsSection', () => {
 
   it('cancels the add card back to the add button', async () => {
     await mountSection()
-    fireEvent.click(screen.getByText(`+ ${en.add}`))
+    fireEvent.click(screen.getByText(en.add))
     await screen.findByLabelText(en.provider)
     fireEvent.click(screen.getAllByText(en.cancel)[1] as HTMLElement)
-    await screen.findByText(`+ ${en.add}`)
+    await screen.findByText(en.add)
     expect(screen.queryByLabelText(en.provider)).toBeNull()
   })