feat(ml-cellar): add materialize command

[scepter914]

Summary

This PR add materialize command.

Change point

• feat(ml-cellar): add materialize command

[Copilot]

Pull request overview

This PR adds two new commands to the ml-cellar CLI for materializing Git LFS files: materialize-all to pull all LFS-managed files, and materialize to pull specific files or directories.

Changes:

• Add new materialize.rs module with materialize_all() and materialize() functions
• Integrate materialize commands into the CLI command structure
• Update README documentation to reflect the new command names (replacing get-all and get with materialize-all and materialize)

Reviewed changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated no comments.

File	Description
src/bin/ml-cellar/materialize.rs	New module implementing Git LFS pull operations for materializing files
src/bin/ml-cellar/main.rs	Add MaterializeAll and Materialize command variants and route them to the materialize module
README.md	Update documentation to use new materialize command names instead of get commands

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