fix : build-time validation for dynamic slug name conflicts in app routes

[naaa760]

What?

• Fail next build when app routes have mismatched dynamic slug names at the same path depth.

Why?

• These conflicts currently slip past validateAppPaths, then crash next start at runtime.

How?

• Run getSortedRoutes(appPaths) inside validateAppPaths and add a unit test for the sibling-slug mismatch case.

Closes NEXT-

Fixes : #91628

[nextjs-bot]

Allow CI Workflow Run

• approve CI run for commit: 7397ee5

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

[nextjs-bot]

Allow CI Workflow Run

• approve CI run for commit: 7397ee5

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer