Remote Functions: Nested routes resolve incorrectly on redirect

Describe the bug

This issue was first introduced in v2.65.1 where navigations from a nested route would resolve incorrectly when a redirect is thrown from a remote function.

e.g. navigating from /some/nested/route to /foo would resolve to /some/nested/foo

I'm guessing this PR #16014 may have been the one to introduce this bug.

Reproduction

1. Clone the repro git clone https://github.com/AdrianGonz97/broken-nested-route-navigation.git or visit the StackBlitz repro
2. Run pnpm install and pnpm dev
3. Navigate to the root page and click Go to Login Page
4. Press Login (this should navigate the page to /nested/foo/bar)
5. Refresh the page (on StackBlitz, right click in the iframe preview and press Reload frame instead)
6. Press Logout (note how the page navigates to /nested/foo/login instead of /login)

Logs

System Info

System:
    OS: Linux 6.8 Ubuntu 24.04.3 LTS 24.04.3 LTS (Noble Numbat)
    CPU: (20) x64 QEMU Virtual CPU version 2.5+
    Memory: 18.62 GB / 31.34 GB
    Container: Yes
    Shell: 5.9 - /usr/bin/zsh
  Binaries:
    Node: 24.11.1 - /home/koala/.volta/tools/image/node/24.11.1/bin/node
    Yarn: 1.22.22 - /home/koala/.volta/tools/image/yarn/1.22.22/bin/yarn
    npm: 11.6.2 - /home/koala/.volta/tools/image/node/24.11.1/bin/npm
    pnpm: 10.33.4 - /home/koala/.volta/bin/pnpm
  npmPackages:
    @sveltejs/adapter-auto: ^7.0.1 => 7.0.1 
    @sveltejs/kit: ^2.63.0 => 2.69.1 
    @sveltejs/vite-plugin-svelte: ^6.0.0 => 6.2.4 
    svelte: ^5.56.1 => 5.56.4 
    vite: ^7.0.0 => 7.3.6

Severity

blocking an upgrade

Additional Information

No response

Start with the linked broken-nested-route-navigation reproduction: run pnpm install and pnpm dev, then follow the login and logout navigation steps. Trace the remote-function redirect from the nested route and add a regression check for the expected /login destination rather than /nested/foo/login.