feat: expose CAS client factory and chunk cache re-exports (#730)

## Context

These changes support the hf-mount project, which needs direct access to
CAS client types.

## Summary

- Changed `create_remote_client` visibility from `pub(crate)` to `pub`
- Added re-exports for `CasClient`, `ChunkCache`, `CacheConfig`, and
`get_cache` in `xet_data::processing`

xet_data/src/processing/mod.rs

@@ -14,6 +14,9 @@ mod xet_file;
 pub use file_cleaner::{Sha256Policy, SingleFileCleaner};
 pub use file_download_session::FileDownloadSession;
 pub use file_upload_session::FileUploadSession;
+pub use remote_client_interface::create_remote_client;
+pub use xet_client::cas_client::Client as CasClient;
+pub use xet_client::chunk_cache::{CacheConfig, ChunkCache, get_cache};
 pub use xet_file::XetFileInfo;
 
 pub use crate::deduplication::RawXorbData;

xet_data/src/processing/remote_client_interface.rs

@@ -5,7 +5,7 @@ use xet_client::cas_client::{Client, RemoteClient};
 use super::configurations::TranslatorConfig;
 use crate::error::Result;
 
-pub(crate) async fn create_remote_client(
+pub async fn create_remote_client(
     config: &TranslatorConfig,
     session_id: &str,
     dry_run: bool,