feat: implement model downloads from huggingface

[bsbds]

No description provided.

[rogercloud]

Thanks for the PR — the multi-provider abstraction (_candidate_remote_providers / _resolve_remote_location / _download_remote_repo) is clean and the auto-fallback logic is correct.

I'm requesting changes on a few issues:

Critical:

• The "remote" alias silently remaps from ModelScope to HuggingFace. Users with DEEPDOC_MODEL_PROVIDER=remote will be rerouted without warning. Please either preserve the old mapping or document this as a breaking change.

Major:

• _normalize_provider is duplicated in config.py and model_store.py. This PR extends both copies, making the duplication riskier. Consider exporting from one location.
• auto provider now prefers HuggingFace over ModelScope (both scan and download). Previously auto only used ModelScope. This should be called out explicitly.
• Error messages lost diagnostic detail — the old message listed expected files, env var names, and search paths. The new generic message makes debugging harder.
• CLI default changed from modelscope to huggingface in both --provider and download_all().

Minor (test gaps):

• No test for auto discovering pre-downloaded HF artifacts (only MS pre-download is tested).
• No test for HF per-bundle env override (e.g. DEEPDOC_HUGGINGFACE_VISION_REPO).
• huggingface_repo_env: str = "" default silently skips per-bundle HF env vars via os.getenv("") → None for custom BundleSpecs.
• The backward-compat repo_env / repo_default / etc. properties delegate to modelscope fields. Consider updating the one test reference (ms.BUNDLES["vision"].repo_env) directly and removing the properties.

[rogercloud]

"remote" alias silently remapped (critical)

"remote" was previously mapped to "modelscope". Changing it to "huggingface" means any user with DEEPDOC_MODEL_PROVIDER=remote will be silently rerouted to HuggingFace after upgrading.

This is particularly impactful for users in regions where HF access is restricted.

Suggestion: Either preserve "remote" → "modelscope" for backward compatibility, or document this as an explicit breaking change.

[rogercloud]

auto provider priority changed from ModelScope-first to HF-first (major)

Previously auto only tried ModelScope. Now it tries HuggingFace first for both scanning pre-downloaded artifacts and downloading. This means:

1. Pre-downloaded MS files that previously satisfied auto will be tried after HF files
2. New downloads go to the HF cache path

This is a bigger behavioral change than just "adding HF support" and should be called out explicitly.

[rogercloud]

Error message lost diagnostic detail (major)

The old error listed: expected files, relevant env var names (per-bundle and global), and search paths. This was very helpful for debugging misconfigurations.

The new aggregated error is generic: "Failed to resolve bundle 'X'. ...". Consider including the expected files list and relevant env var names in the aggregated error, e.g.:

raise FileNotFoundError(
    "Failed to resolve bundle '{}' (expected files: {}). {}".format(
        spec.name,
        ", ".join(spec.required_files),
        " ".join(failures),
    )
)

[rogercloud]

huggingface_repo_env: str = "" is a minor footgun

When huggingface_repo_env is "", os.getenv("") returns None, silently skipping per-bundle HF env var resolution. All current BUNDLES entries override this, so it works today — but anyone adding a custom BundleSpec without specifying huggingface_repo_env would get silent behavior.

Consider using a sentinel value or documenting the empty-string default more clearly.

[rogercloud]

_normalize_provider is duplicated (major)

The same function (with the same aliases) exists in both config.py and model_store.py. This PR extends both copies identically, which works but increases the risk of them diverging in the future.

Consider exporting _normalize_provider from model_store.py and importing it here, or vice versa.

[rogercloud]

Default provider changed from modelscope to huggingface (major)

Both the CLI --provider default and the download_all() function default changed. Existing users running deepdoc-download-models with no args will download from HuggingFace instead of ModelScope.

The README does note the new default, which is good. Just flagging this as a breaking default change for awareness.