Fix typegen for star folder fs routes

[puneetdixit200]

Fixes #14744.

This updates filesystem route path generation so a folder route module in routes/*/route.tsx is treated as a splat route while keeping the route id and file path unchanged for generated type imports. Filenames like routes/*.tsx remain unsupported, matching the existing raw * filename rules.

Tests run:

• pnpm --filter @react-router/fs-routes build
• pnpm --filter @react-router/fs-routes typecheck
• pnpm test -- --selectProjects fs-routes --runTestsByPath packages/react-router-fs-routes/__tests__/flatRoutes-test.ts
• pnpm test:integration:run integration/typegen-test.ts --project=chromium -g "splat|route file in literal star folder"
• pnpm exec prettier --check packages/react-router-fs-routes/flatRoutes.ts packages/react-router-fs-routes/__tests__/flatRoutes-test.ts integration/typegen-test.ts packages/react-router-fs-routes/.changes/patch.star-folder-splat.md
• pnpm changes:validate
• git diff --check

[remix-cla-bot]

Hi @puneetdixit200,

Welcome, and thank you for contributing to React Router!

Before we consider your pull request, we ask that you sign our Contributor License Agreement (CLA). We require this only once.

You may review the CLA and sign it by adding your name to contributors.yml.

Once the CLA is signed, the CLA Signed label will be added to the pull request.

If you have already signed the CLA and received this response in error, or if you have any questions, please contact us at hello@remix.run.

Thanks!

- The Remix team

[github-actions]

✅ Change File Found

A change file file exists in this PR. Thanks!

[remix-cla-bot]

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳