improve shx upload error handling

README.md

@@ -7,7 +7,7 @@ tiny helper repo for uploads to the SHX Zipline instance.
 - `bin/shx-upload` - upload one or more files to Zipline
 - `.gitea/workflows/ci.yml` - basic CI for syntax + smoke tests
 - `.gitea/workflows/release.yml` - tag build artifact packaging
-- `tests/smoke.sh` - local smoke test with mocked network calls
+- `tests/smoke.sh` - local smoke tests covering success, failures, and request formation with mocked network calls
 
 ## requirements
 
@@ -50,6 +50,8 @@ push a tag like `v0.1.0` to trigger the release packaging workflow.
 
 - username/password are for dashboard login only
 - actual uploads use a Zipline API token
+- failed uploads now print the Zipline response body when one is returned
+- successful uploads are validated to ensure the response includes a non-empty `.files` array
 - docs: https://zipline.diced.sh/docs
 - upload endpoint ref: https://v3.zipline.diced.sh/docs/api/upload
 - shell uploader guide: https://zipline.diced.sh/docs/guides/uploaders/shell-script