fix: resolve aliases from referenced tsconfig projects in sibling directories

[benpsnyder]

Fixes #190.

Summary

When a root tsconfig uses project references (e.g., Nuxt, shared config packages), the referenced configs may live in sibling directories (.nuxt/, .config/) that are never visited by the ancestor directory walk in getResolvers. Imports using aliases defined in those referenced projects fail with configMismatch.

Example: Nuxt generates .nuxt/tsconfig.app.json with path aliases like @: ["../app"]. A file at tests/mytest.ts importing @/something fails because:

1. The walk from tests/ goes up to the project root
2. The root tsconfig.json has "files": [] — skipped (no resolver created)
3. .nuxt/tsconfig.app.json is stored under .nuxt/ in the cache — never visited

Changes

getResolvers — when visiting a directory, also yield resolvers from referenced projects. This surfaces aliases from sibling directories without changing the walk itself.

createResolver — accepts a skipIncludeCheck flag. Referenced resolvers skip the include/exclude check since the parent project's scope applies rather than the reference's narrow include patterns (which typically only cover its own source files).

File	Change
src/resolver.ts	getResolvers yields referenced resolvers; createResolver supports skipIncludeCheck; unrestrictedResolversByProject WeakMap
test/__fixtures__/referenced-sibling/	Test fixture: root tsconfig with files: [] referencing .config/tsconfig.app.json that defines @/* paths

Test plan

• New referenced-sibling fixture passes (both tsc and Vite build)
• All 7 existing test fixtures continue to pass
• Verify with a real Nuxt project that uses .nuxt/tsconfig.app.json references