[Bug] Axis tooltip throws "reading 'getDataParams'" when a merged setOption removes series

### Version

6.1.0 (also on master @ 30076ae)

### Link to Minimal Reproduction

https://github.com/JoshuaKGoldberg/repros/tree/echarts-tooltip-stale-series-index

### Steps to Reproduce

```shell
npm install
npm run build
npm run repro:headless
```

Or `npm run repro:browser` to drive it by hand. The repro is:

1. `echarts.init` a chart with `tooltip: {trigger: 'axis'}`, a category `xAxis`, and 5 `line` series (`animation: false`).
2. Hover the middle of the chart so the axis tooltip shows.
3. Without moving the pointer off the chart, `setOption` the same option with only 1 series, in merge mode:

```js
chart.setOption(optionWithOneSeries, {
lazyUpdate: false,
notMerge: false,
replaceMerge: ['series', 'xAxis', 'yAxis'],
});
```

### Current Behavior

An uncaught `TypeError` is thrown a tick later:

```plaintext
Uncaught TypeError: Cannot read properties of undefined (reading 'getDataParams')
at TooltipView._showAxisTooltip
at TooltipView._tryShow
at TooltipView.manuallyShowTip
at
```

Poking deeper:

1. `TooltipView` caches the last hovered pointer state in `_lastX` / `_lastY` / `_lastDataByCoordSys`, and `_lastDataByCoordSys` holds raw `seriesIndex` numbers.
2. Every `setOption` runs `TooltipView.render()` → [`_keepShow()`](https://github.com/apache/echarts/blob/6.1.0/src/component/tooltip/TooltipView.ts#L240-L274), which, when `_lastX`/`_lastY` are set and `triggerOn` is neither `'none'` nor `'click'`, schedules `setTimeout(() => self.manuallyShowTip(..., {x: _lastX, y: _lastY, dataByCoordSys: _lastDataByCoordSys}))` to re-show the tooltip after the update.
3. The new option has fewer series than those cached indices refer to. [`GlobalModel.getSeriesByIndex`](https://github.com/apache/echarts/blob/6.1.0/src/model/Global.ts#L764-L766) is just `this._componentsMap.get('series')[seriesIndex]`, so an out-of-range index yields `undefined`, and [`_showAxisTooltip`](https://github.com/apache/echarts/blob/6.1.0/src/component/tooltip/TooltipView.ts#L579-L582) dereferences it unguarded:

```ts
each(axisItem.seriesDataIndices, function (idxItem) {
const series = ecModel.getSeriesByIndex(idxItem.seriesIndex);
const dataIndex = idxItem.dataIndexInside;
const cbParams = series.getDataParams(dataIndex) as TooltipCallbackDataParams; // series is undefined
```

This only reproduces under merge mode. With `setOption(option, true)` the tooltip component view is disposed and recreated, so `_lastX` is cleared and nothing throws. It needs the combination the repro uses: the `tooltip` component is **merged** (the view survives with its stale cache) while `series` is **replaced** (the cached indices go out of range).

It is not fatal but:

- The stale tooltip stays on screen listing all 5 removed series with their old values.
- Every subsequent `setOption` throws again while the pointer sits still (3 updates → 3 errors).
- Moving the pointer recovers it: the tooltip re-renders with the remaining series and no further errors occur.

Because the throw comes from a `setTimeout`, it can't be caught by application code.
It lands as an uncaught error, so any app with error reporting sees it as a user-visible crash even though the chart survives.
That's how I landed here!

### Expected Behavior

The re-shown tooltip skips series that no longer exist instead of throwing.

ECharts already applies exactly this guard at the sibling call site that builds axis-pointer label params, [`src/component/axisPointer/viewHelper.ts#L177-L180`](https://github.com/apache/echarts/blob/6.1.0/src/component/axisPointer/viewHelper.ts#L177-L180):

```ts
zrUtil.each(seriesDataIndices, function (idxItem) {
const series = ecModel.getSeriesByIndex(idxItem.seriesIndex);
const dataIndex = idxItem.dataIndexInside;
const dataParams = series && series.getDataParams(dataIndex);
dataParams && params.seriesData.push(dataParams);
});
```

### Environment

- **OS**: macOS 15
- **Browser**: Chromium 151 (also reproduces in headless Chromium via Playwright)
- **Framework**: none (plain `echarts.init`)

### Any additional comments?

A few lines above the crash, [`TooltipView.ts#L556-L562`](https://github.com/apache/echarts/blob/6.1.0/src/component/tooltip/TooltipView.ts#L556-L562) dereferences `axisModel` *before* its own null check:

```ts
const axisModel = ecModel.getComponent(axisItem.axisDim + 'Axis', axisItem.axisIndex) as AxisBaseModel;
const axisValue = axisItem.value;
const axis = axisModel.axis; // throws if axisModel is undefined
const axisValueParsed = axis.scale.parse(axisValue);
if (!axisModel || axisValue == null) { // too late
return;
}
```

The same staleness that removes a series can remove an axis, so `getComponent` can return `undefined` here.

Related but distinct:

* #19827: same `_keepShow` re-show path, but a null tooltip DOM on the *item* tooltip path
* #21535: `getDataParams` crashing from `findEventDispatcher` mousemove on a disposed series

Start with src/component/tooltip/TooltipView.ts, especially _keepShow() and _showAxisTooltip(), and compare the existing guard in src/component/axisPointer/viewHelper.ts. Run the linked reproduction with npm install, npm run build, and npm run repro:headless; done means merged series or axes removed by setOption no longer cause an uncaught error and stale tooltip entries are skipped.

Written by the indexing model from the issue text.