Link `to` property type signature does not support number/delta usage

[sean-perkins]

I'm using React Router as a...

library

Reproduction

1. Go to https://stackblitz.com/edit/github-sedw5gxm?file=app%2Froutes%2Fhome.tsx
2. Click "Click me"
3. Observe: Navigation back occurs correctly
4. Re-open https://stackblitz.com/edit/github-sedw5gxm?file=app%2Froutes%2Fhome.tsx or navigate forward
5. Open home.tsx
6. Observe: The manual type cast to the to property
7. Remove the type cast
8. Observe: Type error for the to property

System Info

System:
    OS: macOS 15.1
    CPU: (12) arm64 Apple M4 Pro
    Memory: 151.52 MB / 24.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.13.1 - ~/.volta/tools/image/node/22.13.1/bin/node
    npm: 10.9.2 - ~/.volta/tools/image/node/22.13.1/bin/npm
    pnpm: 9.15.0 - ~/.volta/bin/pnpm
    bun: 1.1.38 - /opt/homebrew/bin/bun
  Browsers:
    Chrome: 133.0.6943.142
    Safari: 18.1
  npmPackages:
    @react-router/dev: ^7.1.1 => 7.1.3 
    @react-router/node: ^7.1.1 => 7.1.3 
    @react-router/serve: ^7.1.1 => 7.1.3 
    react-router: ^7.1.1 => 7.1.3 
    vite: catalog: => 6.0.11

Used Package Manager

pnpm

Expected Behavior

Developers can assign a number to the to property of Link to do delta navigation.

<Link to={-1}>Click me</Link>

Actual Behavior

The Link component only supports a string type for the to property, while being built around the history API that supports the delta usage.

The runtime behavior is correct with this usage:

<Link to={-1 as unknown as string}>Click me</Link

however developers shouldn't need to cast around the restrictive types.

[timdorr]

While this technically works from a functionality perspective, to must be a string so we can render a plain <a> and it's href as a fallback. That is not possible with a number.