fix(core): enhance sandbox usability and fix build error (#24460)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/core/src/services/sandboxedFileSystemService.test.ts

@@ -47,6 +47,10 @@ class MockSandboxManager implements SandboxManager {
   parseDenials(): undefined {
     return undefined;
   }
+
+  getWorkspace(): string {
+    return '/workspace';
+  }
 }
 
 describe('SandboxedFileSystemService', () => {