fix: resolve import paths in additional .ts files

[viktorkombov]

Description:
Fixes broken relative imports in generated StackBlitz samples where additional .ts files (e.g. grid-finjs.component.ts) reference other additional files (e.g. prevent-scroll.directive.ts).

• Extend _modifyImports file filter to include .ts files without explicit fileExtension property
• Fix provider import extraction to correctly handle arguments (e.g. provideRouter([]))

Root cause: _getAdditionalFiles creates LiveEditingFile instances without setting the fileExtension constructor parameter, so the fileExtension === 'ts' filter silently excluded them from import path resolution.