test(tools): add unit tests for error handling functions

* Implement tests for error functions like errRequiredField, errInvalidField, and errEntityNotFound.
* Ensure proper metadata is returned for various error scenarios.
* Validate error handling in CRM, Files, and other tools.
* Introduce tests for parsing stored file IDs and UUIDs.
* Enhance coverage for helper functions related to project resolution and session management.

internal/app/llm_test.go

@@ -15,7 +15,9 @@ func TestServeLLMInstructions(t *testing.T) {
 	serveLLMInstructions(rec, req)
 
 	res := rec.Result()
-	defer res.Body.Close()
+	defer func() {
+		_ = res.Body.Close()
+	}()
 
 	if res.StatusCode != http.StatusOK {
 		t.Fatalf("status = %d, want %d", res.StatusCode, http.StatusOK)