fix(layout): pin shell side panels to px so a window resize can't wobble them / 侧栏与终端固定像素尺寸，消除缩放时分割线抖动

[sumanx]

What / 改动内容

The divider between the sidebar and the main area jittered left/right while the window was being resized. Cause: react-resizable-panels writes each panel's size as flex-grow rounded to 3 significant digits (20.83% → "20.8", ~0.5px at 1440px wide), and that rounding error changes with every window width. A sidebar sized through it wobbled sub-pixel on each resize step, however precisely the layout was fed in.

• Size the sidebar and aux panels (and the terminal, vertically) with a px flex-basis through the Panel style prop, which overrides the library's computed style, and let the center / workspace pane take the remainder. The library's layout is still kept in step — it drives handle drags and min/max clamping, and a drag reaches the px values through the existing onLayout → setWidth / setHeight path.
• Convert px ↔ percent against the space left after the 1px dividers rather than the container width, and compare re-applied layouts at sub-pixel precision (the old 0.25% tolerance skipped small steps until they added up, then snapped).
• Apply the layout in layout effects, and ignore the onLayout calls a container resize itself causes so they are not persisted as a user resize.
• Keep the pane contents (sidebar, aux panel, terminal, workspace) as stable elements, so the shell re-rendering on each resize step skips their subtrees.
• The panel slide transition now covers flex-basis too, since that is what changes when a side panel opens or closes.

Only src/app/workspace/layout.tsx and one rule in globals.css change.

Testing / 测试

• pnpm lint ., pnpm test (560 files / 8390 tests) and pnpm build pass.
• Checked by hand in the desktop app: dragging the window edges no longer moves the sidebar divider. Layout is not covered by the jsdom tests, so dragging the sidebar / aux / terminal dividers and the panel slide animation (which now transitions flex-basis) deserve a quick look from a reviewer.
• Tested on Linux only (GNOME / Wayland, WebKitGTK desktop build); not tried on macOS or Windows.

---

中文说明

调整窗口大小时，左侧栏与主框架之间的分割线会左右抖动。原因：react-resizable-panels 把每个面板的尺寸写成保留 3 位有效数字的 flex-grow（20.83% 变成 "20.8"，1440px 宽时约差 0.5px），而这个舍入误差会随窗口宽度不断变化，所以即使传入的布局再精确，侧栏也会在亚像素级别来回晃动。

• 侧栏、右侧面板（竖向的终端同理）通过 Panel 的 style 用像素的 flex-basis 定宽（它会覆盖库计算出的样式），中间 / 工作区面板占满剩余空间。库的布局仍保持同步，用于拖动分割线和最小/最大宽度限制；拖动结果经由现有的 onLayout → setWidth / setHeight 写回像素值。
• 像素与百分比的换算改为基于“扣除 1px 分割线后的剩余空间”，重新应用布局时的比较精度提高到亚像素（旧的 0.25% 容差会跳过小幅变化，累积后再一次性校正）。
• 在 layout effect 中应用布局，并忽略由容器尺寸变化自身引起的 onLayout，避免被当作用户拖动而持久化。
• 侧栏、右侧面板、终端、工作区内容改为稳定的元素，外壳在每一步缩放时重渲染会跳过它们的子树。
• 面板滑动动画的过渡同时覆盖 flex-basis，因为打开/收起侧栏时变化的就是它。

只改动 src/app/workspace/layout.tsx 和 globals.css 中的一条规则。

测试：pnpm lint .、pnpm test（560 个文件 / 8390 个用例）、pnpm build 均通过。在桌面端手动验证：拖动窗口边缘时侧栏分割线不再移动。布局部分没有被 jsdom 测试覆盖，拖动侧栏 / 右侧面板 / 终端分割线以及面板的滑动动画（现在过渡的是 flex-basis）建议审查时再看一下。仅在 Linux（GNOME / Wayland、WebKitGTK 桌面版）测试，未在 macOS、Windows 上试过。

🤖 Generated with Claude Code

[xintaofei]

codeg work task 294 is done — #897 (2 files, +79/-39).