feat: add tsconfig.json extends resolution to project detection

[jonaslagoni]

Enhancement Request

The automatic project detection in detectTypeScriptImportExtension currently reads tsconfig.json directly but does not resolve the extends field. This means projects using base configurations (e.g., "extends": "@tsconfig/node18/tsconfig.json") won't have their moduleResolution detected if it's defined in the parent config.

Background

Introduced in PR #344, the basic detection works for many cases where moduleResolution is directly in tsconfig.json. However, many real-world TypeScript projects use base configurations via the extends field.

Scope

Add recursive tsconfig resolution to:

1. Read the extends field from tsconfig.json
2. Load and parse the base config (can be a local file or npm package)
3. Merge compilerOptions with proper precedence (child overrides parent)
4. Support multiple levels of inheritance (base can extend another base)

Example Use Cases

Projects using:

• @tsconfig/node18, @tsconfig/node20, etc.
• ./tsconfig.base.json in monorepos
• Custom shared configs

Implementation Notes

• Handle both relative paths (./tsconfig.base.json) and npm packages (@tsconfig/node18/tsconfig.json)
• Use proper Node.js resolution for npm packages
• Implement proper merge logic (arrays override, objects shallow merge)
• Add tests for common scenarios

Related

• Requested in PR feat: add automatic project setup detection to generator lifecycle #344 review: feat: add automatic project setup detection to generator lifecycle #344 (comment)
• Original feature: Add automatic project setup detection to generator lifecycle #336