Function resolveTsConfig

resolveTsConfig(rootPath: string): TsConfigResolution | null
Resolve the tsconfig that should back a ts-morph Project for rootPath. Shared tsconfig discovery used by the kernel factory and every MCP tool that builds a ts-morph Project.
Parameters
- rootPath: string
  Project root directory.
Returns TsConfigResolution | null
The selected config with file count and reason, or null when no candidate exists.
Remarks
Angular CLI workspaces often use a "solution style" root tsconfig.json with "files": [] plus references to tsconfig.app.json / tsconfig.spec.json. Loading such a root config yields an (almost) empty program, so every investigation tool would silently search nothing. The resolver therefore prefers a config that actually contains source files:
1. the first existing candidate, if it has files
2. its references (recursively, *.app.* configs first, *.spec.* last)
3. tsconfig.app.json (root, then src/)
4. any other existing candidate with files
5. the first existing candidate (legacy behaviour)
The same selection order is mirrored in adapter-mcp's tools/helpers/find-ts-config.ts, which decides "has files" from the raw config JSON instead of the TypeScript API (the adapter test suites mock node:fs and @angular-modernizer/core).
Example
```
const resolution = resolveTsConfig('/path/to/angular-project');
// { path: '/path/to/angular-project/tsconfig.app.json', fileCount: 1, reason: 'reference', ... }
```