typedRoutes don't recognize parameter on rewritten url if preceded by path character

### Link to the code that reproduces this issue https://codesandbox.io/p/devbox/elastic-lucy-jfpczm?file=%2F.next%2Ftypes%2Flink.d.ts ### To Reproduce The error is in the generated types file. ### Current vs. Expected behavior If rewriting /@:username to /user/:username, I'd expect a generated type like `/@${SafeSlug<T>}` but instead I get `/@[username]`. ### Provide environment information ```bash Operating System: Platform: darwin Arch: x64 Version: Darwin Kernel Version 21.6.0: Mon Feb 19 20:24:34 PST 2024; root:xnu-8020.240.18.707.4~1/RELEASE_X86_64 Available memory (MB): 16384 Available CPU cores: 8 Binaries: Node: 22.2.0 npm: 10.7.0 Yarn: N/A pnpm: 7.33.7 Relevant Packages: next: 14.2.0 // There is a newer version (14.2.4) available, upgrade recommended! eslint-config-next: 14.2.0 react: 18.3.1 react-dom: 18.3.1 typescript: 5.4.5 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) TypeScript ### Which stage(s) are affected? (Select all that apply) next dev (local) ### Additional context _No response_