Merge pull request #448 from chendefine/fix/panel-host-scroll-jump

fix(shell): keep an overflow:hidden fallback beneath clip (old-engine compat) + guard the cascade

docs/external-plugin-guide.md

@@ -752,7 +752,7 @@ ctx.effect(() =>
 
 - **面板表面**：右/底面板背景 = `var(--dsw-alias-bg-layer-1)`。**绝不消费 `--dsw-specific-sidebar-fill`**（宿主左导航专属，皮肤按左导航语义覆盖它，面板消费会失去填充）。换面板表面 = 覆写 `--dsw-alias-bg-layer-1`。
 - **终端/编辑器表面**：`effectiveTokenValue` 读 `--dsw-alias-bg-base`——`transparent` 与 alpha < 0.9 的半透明值回退不透明底色（文字不叠背景画，issue #90）；≥ 0.9 放行。
-- **根锚点**：宿主 div 带 `data-dsh-better-sidebar`（append 到 body）；其内**面板宿主层** `[data-dsh-panel-host]`（`fixed; inset:0; z-25; pointer-events:none`，v0.13.1+），面板/开关簇 absolute 定位，免疫中间层 transform 劫持；页面级 transform 触发 `data-dsh-panel-host-degraded` 降级。皮肤作用域覆盖限定在 `[data-dsh-better-sidebar]` 内。
+- **根锚点**：宿主 div 带 `data-dsh-better-sidebar`（append 到 body）；其内**面板宿主层** `[data-dsh-panel-host]`（`fixed; inset:0; z-25; pointer-events:none; overflow:hidden+clip`，v0.13.1+），面板/开关簇 absolute 定位，免疫中间层 transform 劫持；页面级 transform 触发 `data-dsh-panel-host-degraded` 降级。`overflow` 级联是**契约**（`hidden` 兜底 + `clip` 收尾，`tests/panel-host-css.spec.ts` 守护）：`hidden` 盒子仍是滚动容器，脚本滚动或浏览器 scroll-into-view 修正（焦点移入视口外区域、嵌套 iframe/工作台加载时抢焦点、面板滑出动画中 focus() 落点）会沿最近可滚祖先滚走整层——面板与开关簇集体偏离视口角（computed left/right 仍"正确"，偏移藏在盒子自身 scroll offset 里）；`clip` 裁剪语义相同但不产生滚动盒，任何路径都滚不动这层。皮肤作用域覆盖限定在 `[data-dsh-better-sidebar]` 内。
 - **布局变量**（`<html>` 上，面板打开时有效）：`--dsh-sidebar-width` / `--dsh-sidebar-height`。右面板宽度 = AppFrame 的 `padding-right` 预留（新版 `#root [data-dsh-frame]` / rc.8 `#root > [data-slot="root"] > div` 双锚点），AppFrame border box 保持完整桌面视口宽度（Harness 以此判定桌面/窄屏布局，避免插件面板展开误入窄屏）；AppFrame 的 details 拖拽手柄按同一变量向左平移贴合列边缘。底部面板仍走 centerCol `margin-bottom`；centerCol 锚点 = **JS 标注**（禁止 `nth-child`）：侧栏 shell 的定位器给测得的 centerCol 节点打 `[data-dsh-center-col]` 标签（`Sidebar.tsx` locate，节点更换/HMR 时随 ref 迁移），`layout.css` 用 `#root [data-dsh-center-col]` 选中（`drag-layout.e2e.ts` 断言恰一节点且为 `[data-slot="conversation"]` 的父级；frame 宽度与桌面 Session Log 由 `desktop-layout.e2e.ts` 断言）。
 - **桌面信号与标题栏**（v0.14.1+ 四方案模型 `SidebarPrefs.titleBarScheme`，唯一决策点 `src/client/titlebar-strip.ts` 纯函数）：
   - 壳信号（只读，不自动触发修改）：URL `dsh-desktop-mode` / `dsh-desktop-platform` / 可选 `dsh-desktop-titlebar-inset`（0–120 clamp）。

src/client/sidebar.module.css

@@ -48,7 +48,18 @@
      hidden box stays a PROGRAMMATICALLY scrollable container, and a
      scrollIntoView fired from panel content (the file tree's "Show in
      folder" reveal) scrolled the host itself — shifting the whole panel,
-     tab bar included, out of the viewport with no way to scroll back. */
+     tab bar included, out of the viewport with no way to scroll back.
+     The same class covers any scroll-into-view fixup — focus moving into
+     an off-viewport region, a nested iframe/workbench claiming focus
+     while it loads — so the guard belongs on the layer itself, not per
+     call site. The `hidden` declaration BEFORE `clip` is an old-engine
+     fallback, not dead style: engines without `clip` support (Safari < 16)
+     drop the `clip` line, which would leave this box `overflow: visible`
+     — no clipping at all, and the page-draggable regression above
+     returns. With `hidden` first those engines keep the clipping (plus
+     its pre-clip scrollability) while every clip-aware engine applies
+     the later `clip`. */
+  overflow: hidden;
   overflow: clip;
 }
 

tests/panel-host-css.spec.ts

@@ -0,0 +1,47 @@
+/**
+ * The unified panel host layer must clip WITHOUT being a scroll container —
+ * the guard for the "panels / toggle cluster jumped away from the viewport
+ * corner" bug class.
+ *
+ * `overflow: hidden` only clips: the box stays a scroll container, so any
+ * script scroll or the browser's native scroll-into-view fixup (focus moving
+ * into an off-viewport region, a nested workbench/iframe claiming focus
+ * while it loads, focus() landing during a panel's slide-out transition)
+ * walks up to the nearest scrollable ancestor — this layer — and scrolls it,
+ * dragging every panel plus the toggle cluster off the corner while the
+ * computed `left`/`right` still read correct (the offset hides in the box's
+ * own scroll offset). `overflow: clip` declared AFTER `hidden` keeps the
+ * `hidden` fallback for engines without clip support and removes the
+ * scrollability everywhere else; the cascade order is part of the contract.
+ */
+import { readFileSync } from 'node:fs'
+import { describe, expect, it } from 'vitest'
+
+const css = readFileSync('src/client/sidebar.module.css', 'utf8')
+
+/** Body of the `:global([data-dsh-panel-host])` rule (up to the un-indented `}`). */
+const hostRule = css.match(/:global\(\[data-dsh-panel-host\]\) \{([\s\S]*?)\n\}/)?.[1]
+
+/** Strip /* ... *​/ comment blocks so prose mentions don't count as declarations. */
+const stripComments = (cssText: string): string => cssText.replace(/\/\*[\s\S]*?\*\//g, '')
+
+describe('panel host layer css', () => {
+  it('declares the clip cascade: hidden first, clip last', () => {
+    expect(hostRule, 'the [data-dsh-panel-host] rule must exist').toBeDefined()
+    const declarations = stripComments(hostRule!).match(/overflow\s*:\s*\w+/g) ?? []
+    expect(declarations).toEqual(['overflow: hidden', 'overflow: clip'])
+  })
+
+  it('stays the fixed viewport layer (containing block + BFC guarantee)', () => {
+    expect(hostRule).toMatch(/position:\s*fixed/)
+    expect(hostRule).toMatch(/inset:\s*0/)
+  })
+
+  it('does not reintroduce overflow on the degraded (absolute) layer', () => {
+    const degraded = css.match(
+      /:global\(\[data-dsh-panel-host\]\[data-dsh-panel-host-degraded\]\) \{([\s\S]*?)\n\}/,
+    )?.[1]
+    expect(degraded, 'the degraded-mode rule must exist').toBeDefined()
+    expect(degraded).not.toMatch(/overflow\s*:/)
+  })
+})