Replace HubApi downloader with swift-huggingface HubClient

[mattt]

Alternative to #297

[Copilot]

Pull request overview

This PR replaces the existing HubApi download implementation with HubClient from the swift-huggingface package, updating download/progress behavior and adjusting tests accordingly.

Changes:

• Add swift-huggingface as a dependency and import/use HubClient in HubApi.
• Implement HubClient selection (cached/uncached, foreground/background) and add repo-id canonicalization for legacy model IDs.
• Update download-related tests to reflect the new download/progress behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
Sources/Hub/HubApi.swift	Switches file download path to HuggingFace.HubClient, adds progress bridging + repo ID resolution/cache, adjusts HEAD redirect handling by platform.
Tests/HubTests/HubApiTests.swift	Updates assertions and progress expectation handling for the new download/progress behavior.
Package.swift	Adds swift-huggingface dependency and links HuggingFace product into the Hub target.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

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[pcuenca]

My download workaround fixes downloads for regular files but not for Xet ones.

I don't think we can solve this here. The problem, I think, is that copyFileToLocalDirectory should receive a directory destination (not the full file path), while downloadFileWithXet expects a file location.

So we either have to update copyFileToLocalDirectoryIfNeeded to remove the trailing filename (and revert my commit here), or append the filename to xetDestination.

[pcuenca]

The good news is that tests now proceed without deadlocks (after my second workaround) so we can see what's remaining.

[mattt]

@pcuenca

My download workaround fixes downloads for regular files but not for Xet ones.

I don't think we can solve this here. The problem, I think, is that copyFileToLocalDirectory should receive a directory destination (not the full file path), while downloadFileWithXet expects a file location.

So we either have to update copyFileToLocalDirectoryIfNeeded to remove the trailing filename (and revert my commit here), or append the filename to xetDestination.

Whoops, sorry about that. I just opened a PR to fix upstream here: huggingface/swift-huggingface#43

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

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[pcuenca]

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