Handle urls in import path by making vfs not panic on Url paths

[sheetalkamat]

Fixes #1905

[Copilot]

Pull request overview

This PR fixes a panic that occurred when the VFS (Virtual File System) encountered URL paths like "https://deno.land/std@0.208.0/path/mod.ts". The TypeScript compiler's module resolver would crash when trying to resolve imports with absolute URLs because the VFS implementation expected only file system paths.

Changes:

• Modified VFS path handling to recognize and gracefully handle URL paths by detecting negative root lengths and returning the correct positive length
• Updated iovfs.RootFor to return nil for URL roots instead of attempting to create invalid sub-filesystems
• Added compiler tests and integration tests to verify URL imports don't cause crashes

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/vfs/internal/internal.go	Fixed RootLength to handle negative values (URLs) by using bitwise NOT operation to convert to positive length
internal/vfs/iovfs/iofs.go	Added URL detection in RootFor to return nil instead of panicking when trying to create sub-filesystem for URLs
testdata/tests/cases/compiler/importUrl.ts	Minimal test case with a URL import to verify no crash occurs
testdata/tests/cases/compiler/importUrlNodeModulesExist.ts	Test case with URL import and existing node_modules to verify resolution behavior
internal/project/untitled_test.go	Integration test that verifies URL imports work in untitled files without crashing
testdata/baselines/reference/compiler/*.{types,symbols,js,trace.json}	Baseline files showing expected behavior: URLs are skipped during module resolution