fix(downloader): list supported URL schemes in DownloadFile error (#9689)

* fix(downloader): list supported URL schemes when input is unrecognized

The error message previously read "does not look like an HTTP URL",
but the downloader actually supports file://, huggingface://, hf://,
ollama://, oci://, and github:// in addition to http(s)://. Users who
type a bare filename or a typo'd scheme (e.g. fle:// instead of file://)
get the misleading impression that only HTTP is accepted.

Reference the existing prefix constants directly via strings.Join so
the scheme list cannot drift when new prefixes are added.

Refs #9683.

Signed-off-by: Tai An <antai12232931@outlook.com>

* fix(downloader): normalize uri.go to LF line endings

Resolves the noisy diff and golangci-lint errcheck warnings on lines I did not actually modify.

* fix(downloader): preserve trailing newline at end of file

---------

Signed-off-by: Tai An <antai12232931@outlook.com>

Author: Anai-Guo

pkg/downloader/uri.go

@@ -467,7 +467,7 @@ func (uri URI) DownloadFileWithContext(ctx context.Context, filePath, sha string
 		}
 	} else if !os.IsNotExist(err) || !URI(url).LooksLikeHTTPURL() {
 		// Error occurred while checking file existence
-		return fmt.Errorf("file %s does not exist (%v) and %s does not look like an HTTP URL", filePath, err, url)
+		return fmt.Errorf("could not fetch %q: local file does not exist (%v) and %q is not a recognized downloadable URL (supported schemes: %s)", filePath, err, url, strings.Join([]string{HTTPPrefix, HTTPSPrefix, LocalPrefix, HuggingFacePrefix, HuggingFacePrefix1, OllamaPrefix, OCIPrefix, OCIFilePrefix, GithubURI2}, ", "))
 	}
 
 	xlog.Info("Downloading", "url", url)