Semi Design Steps: initial={1} breaks onChange — next step click fires nothing

## Summary
On the Semi Design Steps docs page, a `Steps type="basic"` demo using `initial={1}` does not update when another step is clicked. With `onChange={setCurrent}`, clicking Step Two leaves `current` at 1.

## Environment
- Browser: Chromium 151.0.7922.34
- OS: macOS
- Viewport: 1280x720, DPR 1
- Locale: en-US, timezone Europe/Berlin
- Page: `/zh-CN/navigation/steps` (Steps 步骤 - Semi Design)

## Steps to reproduce
1. Open `/zh-CN/navigation/steps` (0s).
2. Scroll to the 默认步骤条（旧版） demo (4.56s).
3. Click the Live code editor, press Cmd+a, then paste the code below (12.05s to 13.69s):
```jsx
const [current, setCurrent] = React.useState(1);
return (
  <div style={{ padding: 24 }}>
    <p style={{ marginBottom: 12, fontSize: 13, color: '#555' }}>
      Current step: <strong>{current}</strong>
    </p>
    <Steps type="basic" initial={1} current={current} onChange={setCurrent}>
      <Steps.Step title="Step One" description="First step" />
      <Steps.Step title="Step Two" description="Second step" />
      <Steps.Step title="Step Three" description="Third step" />
    </Steps>
  </div>
);
```
4. Click **Step Two** in the preview (22.15s), then click it again (27.26s).

## Expected
The click calls `onChange` and `current` changes. Step Two becomes the active step.

## Actual
`Current step` stays at **1** and Step One stays active after both clicks (frames at 25s and 31s). Step Two only shows a hover highlight (23s, 29s).

## Evidence
- 17s: the preview shows `Current step: 1`. Step icons are numbered 2, 3 and 4, as expected with `initial={1}`.
- 22.15s / 27.26s: clicks on the `Step Two` list item. No state change follows.
- 33s: the failing code with `initial={1}` and `useState(1)` is visible.
- 0s console: `TypeError: Cannot read properties of null (reading '/zh-CN')` in `app-11d708dccad1497c7e8f611116.js`. It is logged on load before any interaction, so it is likely unrelated.

## Control (not confirmed)
At 34.19s the code was changed to `useState(0)` with no `initial` prop. Step Two was clicked at 40.98s. The sampled frames do not show the result of that click, so this recording does not confirm whether the variant without `initial` works.

## Suggested area
Check the Steps (`type="basic"`) click handler. Look at how the clicked index is derived and offset by `initial` before it is passed to `onChange`.

*Recorded with SceneRecap.*