[Validation] Scroll position and hash links during enhanced navigation

**Scenario contact:** @javiercn ## Scenario **This scenario validates that two reported bugs are fixed.** Both were filed against .NET 10 enhanced navigation, and both are about the browser ending up somewhere the user did not ask for. * **A same-page anchor still fetched the page.** With `data-enhance-nav="false"` on the navigation container, clicking a link to an anchor on the current page, such as `/#contact-us`, still issued a fetch. Turning enhanced navigation off was meant to leave the browser to scroll natively. ([#63396](https://github.com/dotnet/aspnetcore/issues/63396)) * **Scroll reset ran before the new content rendered.** Navigating from one page to another started the scroll immediately, so the user watched the *old* page scroll past before the new one appeared. ([#64015](https://github.com/dotnet/aspnetcore/issues/64015)) Both are fixed in .NET 11. This validates the fixes, and the surrounding hash-link behavior while you are there. ## Minimum build .NET 11 Preview 7 or later. ## Configurations to cover * Blazor Web App * [x] Static SSR * [x] Interactive Server * [ ] Interactive WebAssembly * [ ] Interactive Auto * [ ] Standalone WebAssembly * [ ] Hybrid (MAUI) Enhanced navigation belongs to Blazor Web Apps. Both reported bugs reproduce with statically rendered pages; Interactive Server is included because a circuit makes the destination content arrive in more stages, which is where the scroll timing bug was visible. ## Also exercise * [ ] Published output * [ ] An existing .NET 10 app upgraded to .NET 11 * [ ] Trimming or ahead-of-time compilation * [ ] More than one server instance, or a proxy in front * [ ] Hot Reload * [ ] An IDE as well as the command line * [ ] Container ## Setup Throttle the network in the browser. The scroll timing bug is only visible when there is a gap between the navigation starting and the content arriving, and on a fast local connection there is not one. ## What to build Two pages, each several screens tall so the scrolling is real, with a heading part way down carrying an anchor such as `#contact-us`. Give the two pages obviously different backgrounds, so you can tell at a glance which one is on screen part way through a navigation. Add two navigation containers holding the same three links: * An ordinary nav menu. * One marked `data-enhance-nav="false"`. The three links are: an anchor on the current page, an anchor on the other page, and the other page with no anchor. ## Things to try The first two are the reported repros. Watch the network tab for the first, and the page itself for the second. * From the `data-enhance-nav="false"` container, click the link to an anchor on the **current** page and watch the network tab. This is the first reported bug. * Scroll to the bottom of page one, then click a plain link to page two and watch what is on screen while the scroll happens. This is the second reported bug. * The same same-page anchor link from the ordinary nav container. * An anchor link pointing at the other page. * Browser back and forward across each of those navigations. * Reloading directly on an address that includes an anchor. ## Expected behavior The browser ends up where the link pointed, and never shows the previous page's content moving on the way there. ### Must hold * Clicking a same-page anchor link inside a `data-enhance-nav="false"` container issues **no request in the network tab**, and the browser scrolls to the anchor natively. * Navigating from the bottom of page one to page two shows no frame of page one's content scrolling. The new content appears first, then the position settles. * An anchor link pointing at the other page loads that page and lands on the named anchor, not at the top. * A plain link to the other page lands at the top of that page. * A same-page anchor link in the ordinary nav container also lands on the anchor. * Browser back and forward return to the positions the user was at. ## Evidence to capture A short screen recording of the throttled navigation between the two long pages. The reported symptom is a flash that a still screenshot cannot show. For the anchor case, a screenshot of the network tab showing no request. ## Documentation to use * [Enhanced navigation and form handling](https://learn.microsoft.com/aspnet/core/blazor/fundamentals/navigation?view=aspnetcore-11.0#enhanced-navigation-and-form-handling) ## What to report Report results using the format described in the [validation testing manual](https://github.com/dotnet/aspnetcore/issues/68479). Include link to a repository with the test app.