feat(KB-141): fix workspace type resolution and add clean-checkout typecheck tests

- Remove dist-dependent workspace type resolution from all tsconfig files

- Add clean-checkout typecheck regression test to CI suite

- Update package.json type definitions for core, engine, dashboard, and cli packages

- Update README with typecheck testing documentation

- Clean up unused test files and component dependencies

packages/dashboard/app/hooks/useFileEditor.ts

@@ -56,7 +56,7 @@ export function useFileEditor(
       setError(null);
 
       try {
-        const response: FileContentResponse = await fetchFileContent(taskId, filePath);
+        const response: FileContentResponse = await fetchFileContent(taskId, filePath!);
 
         if (!cancelled) {
           setContentState(response.content);