fix(desktop): open-with menu viewport-flip + openPreview opens panel

真机验证发现「打开方式」点了没反应：OpenWithMenu 用 top:anchor.bottom+6 无视口翻转，
触发器贴在输入框上方时菜单渲染到输入框后面/视口外 → 改为测量后向上翻转+视口夹取+提高 z-index。
另外 openPreview 只加预览 tab 不开面板，从聊天/卡片触发时面板不显示 → openPreview 现在先 openPanel。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

desktop/src/components/common/OpenWithMenu.test.tsx

@@ -68,4 +68,18 @@ describe('OpenWithMenu', () => {
     fireEvent.mouseDown(document.body)
     expect(onClose).toHaveBeenCalledTimes(1)
   })
+
+  it('flips above the anchor when it would overflow the viewport bottom', () => {
+    // The trigger often sits right above the composer; the menu must not render off-screen below it.
+    Object.defineProperty(window, 'innerHeight', { value: 300, configurable: true })
+    Object.defineProperty(window, 'innerWidth', { value: 1000, configurable: true })
+    const rectSpy = vi.spyOn(HTMLElement.prototype, 'getBoundingClientRect').mockReturnValue({
+      height: 200, width: 220, top: 0, left: 0, right: 0, bottom: 0, x: 0, y: 0, toJSON: () => ({}),
+    } as DOMRect)
+    // anchor near the bottom: top:260/bottom:270. Down would be 276, 276+200=476 > 300-8 ⇒ flip up.
+    render(<OpenWithMenu items={makeItems()} anchor={{ top: 260, bottom: 270, left: 20, right: 120 }} onClose={vi.fn()} />)
+    // flipped top = anchor.top - height - 6 = 260 - 200 - 6 = 54
+    expect(screen.getByRole('menu').style.top).toBe('54px')
+    rectSpy.mockRestore()
+  })
 })

desktop/src/components/common/OpenWithMenu.tsx

@@ -1,5 +1,5 @@
 import { createPortal } from 'react-dom'
-import { useEffect, useRef } from 'react'
+import { useEffect, useLayoutEffect, useRef, useState } from 'react'
 import { Globe, ExternalLink, FileText } from 'lucide-react'
 import { TargetIcon } from './TargetIcon'
 import type { OpenWithItem } from '../../lib/openWithItems'
@@ -17,8 +17,35 @@ function ItemIcon({ item }: { item: OpenWithItem }) {
   return <ExternalLink size={18} strokeWidth={1.9} />
 }
 
+const MARGIN = 8
+
 export function OpenWithMenu({ items, anchor, onClose }: Props) {
   const ref = useRef<HTMLDivElement>(null)
+  // Initial guess; corrected (before paint) by the layout effect once we can measure the menu.
+  const [pos, setPos] = useState<{ top: number; left: number }>(() => ({
+    top: anchor.bottom + 6,
+    left: Math.max(MARGIN, Math.min(anchor.left, window.innerWidth - 240 - MARGIN)),
+  }))
+
+  // Position viewport-aware: flip above the anchor if it would overflow the bottom
+  // (the trigger often sits right above the composer), and clamp into the viewport.
+  useLayoutEffect(() => {
+    const el = ref.current
+    if (!el) return
+    const { height, width } = el.getBoundingClientRect()
+    const vh = window.innerHeight
+    const vw = window.innerWidth
+
+    let top = anchor.bottom + 6
+    if (height > 0 && top + height > vh - MARGIN) {
+      const flipped = anchor.top - height - 6
+      top = flipped >= MARGIN ? flipped : Math.max(MARGIN, vh - height - MARGIN)
+    }
+    let left = anchor.left
+    if (width > 0) left = Math.max(MARGIN, Math.min(left, vw - width - MARGIN))
+    setPos({ top, left })
+  }, [anchor])
+
   useEffect(() => {
     const onDown = (e: MouseEvent) => { if (!ref.current?.contains(e.target as Node)) onClose() }
     const onKey = (e: KeyboardEvent) => { if (e.key === 'Escape') onClose() }
@@ -31,8 +58,8 @@ export function OpenWithMenu({ items, anchor, onClose }: Props) {
     <div
       ref={ref}
       role="menu"
-      className="fixed z-50 min-w-[220px] overflow-hidden rounded-[12px] border border-[var(--color-border)] bg-[var(--color-surface)] py-1 shadow-[var(--shadow-dropdown)]"
-      style={{ top: anchor.bottom + 6, left: Math.min(anchor.left, window.innerWidth - 240) }}
+      className="fixed min-w-[220px] overflow-hidden rounded-[12px] border border-[var(--color-border)] bg-[var(--color-surface)] py-1 shadow-[var(--shadow-dropdown)]"
+      style={{ top: pos.top, left: pos.left, zIndex: 1000 }}
     >
       {items.map((item) => (
         <button

desktop/src/stores/workspacePanelStore.test.ts

@@ -305,6 +305,15 @@ describe('workspacePanelStore', () => {
     ])
   })
 
+  it('openPreview opens the workspace panel when it was closed', async () => {
+    mocks.getWorkspaceFileMock.mockResolvedValue({
+      state: 'ok', path: 'src/a.ts', content: 'export const a = 1', language: 'typescript', size: 18,
+    })
+    expect(useWorkspacePanelStore.getState().isPanelOpen('session-closed-preview')).toBe(false)
+    await useWorkspacePanelStore.getState().openPreview('session-closed-preview', 'src/a.ts', 'file')
+    expect(useWorkspacePanelStore.getState().isPanelOpen('session-closed-preview')).toBe(true)
+  })
+
   it('opens preview tabs, supports multiple kinds, and reuses duplicates without persistence', async () => {
     const storage = typeof globalThis.localStorage === 'undefined' ? null : globalThis.localStorage
     const setItemSpy = storage ? vi.spyOn(storage, 'setItem') : null

desktop/src/stores/workspacePanelStore.ts

@@ -431,6 +431,10 @@ export const useWorkspacePanelStore = create<WorkspacePanelStore>((set, get) =>
   },
 
   openPreview: async (sessionId, path, kind) => {
+    // Ensure the workspace panel is visible — openPreview is now triggered from places
+    // where the panel may be closed (e.g. the chat "打开方式" menu / turn-changes card),
+    // not only from inside the already-open file tree.
+    get().openPanel(sessionId)
     const tabId = getWorkspacePreviewTabId(path, kind)
     const requestKey = makePreviewKey(sessionId, tabId)
     const existing = get().previewTabsBySession[sessionId]?.find((tab) => tab.id === tabId)