fix: update validation return type for unknown pages router

[HimanshuKumarDutt094]

I updated the return type of API routes and route handlers from

Promise | Response | Promise | void

to

Promise<Response | void> | Response | void | unknown

which fixes #82877.
for pages router with trpc the type cannot be determined

  The types returned by 'default(...)' are incompatible between these types.
    Type 'unknown' is not assignable to type 'void | Response | Promise<void | Response>'.

adding unknown fixes this and build work without any issues

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 1e2d00a

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

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 1e2d00a

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

[HimanshuKumarDutt094]

anyone able to verify this? its working on my patch package for nextjs 15 with trpc and next auth.