[bug] Tanstack Router: `parseAsTimestamp` parses defalt value as `1970-01-01T00:00:02.025Z` when reloaded or opened with searchParams

## Context

What's your version of `nuqs`?

```
"nuqs": "^2.7.2"
```

What framework are you using?

- ✅ Other (Tanstack Router)

Which version of your framework are you using?

```
"@tanstack/react-router": "^1.132.0",
"react": "^19.0.0",
"react-dom": "^19.0.0"
```

## Description

**BUG**: When query states is changed to `?from=1760207400000&to=1760812199999` and I reload the page or open the same URL in different tab, it fails to parse the value and changes the url to `?from="1970-01-01T00%3A00%3A02.025Z"&to="1970-01-01T00%3A00%3A02.025Z"`

**EXPECTED**: URL to be same and parse the timestamps correctly.

However this only happens when I add `validateSearch` in route definition
```ts
export const Route = createFileRoute("/")({
component: App,
// THE BUG ONLY HAPPENS WHEN USING validateSearch IF I REMOVE `validateSearch` IT WORKS AS EXPECTED
validateSearch: createStandardSchemaV1(searchParams, {
partialOutput: true,
}),
});
```

## Reproduction

Deployed Version: https://nuqs-repro.pages.dev/
GitHub Repo: https://github.com/mdhruvil/nuqs-repro

- Visit "/"
- Current Week is selected by default, see URL and values displayed on page
- Click on "Set to Previous Week"
- It changes url to select previous week (works as expected)
- Refresh the page or copy url and open in new tab
- It changes url to `?from="1970-01-01T00%3A00%3A02.025Z"&to="1970-01-01T00%3A00%3A02.025Z"` instead of parsing the actual timestamp values

在 Tanstack Router 的路由定義中使用 `validateSearch` 和 `createStandardSchemaV1` 時會發生此 bug。檢查 nuqs 原始碼中的 `parseAsTimestamp` parser，可能位於 parsers 模組中。重現 repository 顯示了這個問題：頁面重新載入時，timestamp 被錯誤地解析為預設日期。檢查 parser 在 hydration 期間如何處理數字 timestamp 與字串序列化之間的差異。執行提供的重現，以查看 URL 的變更。

由索引模型根據 Issue 內容生成。