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

[Anai-Guo]

Summary

Closes #9683.

When DownloadFile is given an input that is neither a local path that exists nor an HTTP-style URL, it returns the error:

file ... does not exist (...) and ... does not look like an HTTP URL

The wording suggests only HTTP URLs are accepted. In reality, LocalAI's downloader also recognizes file://, huggingface:// / hf:// / hf.co/, ollama://, oci://, and github:// (see the constants in pkg/downloader/uri.go and LooksLikeURL).

In #9683 the user typed the bare filename Phi-3-mini-4k-instruct-q4.gguf — none of the supported scheme prefixes match, so the error fires and the message gives no hint about what scheme they should have used (e.g. file:// for a local absolute path or huggingface://microsoft/Phi-3-mini-4k-instruct-gguf for HF).

Change

One-line wording fix in pkg/downloader/uri.go. The new message:

could not fetch %q: local file does not exist (%v) and %q is not a recognized
downloadable URL (supported schemes: http://, https://, file://, huggingface://,
hf://, ollama://, oci://, github://)

No tests assert on the exact phrasing (grep -n "does not look like" pkg/downloader/uri_test.go is empty), so this is a pure UX improvement.

Test plan

• gofmt -l clean
• string isn't asserted in pkg/downloader/uri_test.go
• CI

🤖 Generated with Claude Code

[mudler]

Ideally I'm ok with changing the error message, but instead of duplicating the prefixes accepted, we have constants/prefix already - better use these so we keep it tight and it makes it easier to manage drift long-term

[Anai-Guo]

@mudler thanks for the review — addressed in 6a72a40. The error message now does strings.Join(...) over the existing prefix constants (HTTPPrefix, HTTPSPrefix, LocalPrefix, HuggingFacePrefix, HuggingFacePrefix1, OllamaPrefix, OCIPrefix, OCIFilePrefix, GithubURI2) instead of duplicating the literals, so it can't drift when new schemes are added. Also signed-off the rewritten commit so DCO is green now.