cli: surface HTTP status and body on backend errors

cli/src/main.py

@@ -59,6 +59,11 @@ def save_response(response: httpx.Response, destination: Path) -> None:
     destination.write_bytes(response.content)
 
 
+def format_http_error(response: httpx.Response, endpoint: str) -> str:
+    body = response.text.strip() or "<empty response body>"
+    return f"HTTP {response.status_code} from {endpoint}: {body}"
+
+
 def main() -> int:
     parser = build_parser()
     args = parser.parse_args()
@@ -84,7 +89,7 @@ def main() -> int:
     try:
         response.raise_for_status()
     except httpx.HTTPStatusError as exc:
-        message = exc.response.text.strip() or str(exc)
+        message = format_http_error(exc.response, endpoint)
         parser.exit(1, f"{message}\n")
 
     if args.to_file: