Function process_file_entry 

pub async fn process_file_entry(
    entry: &FileEntry,
    session_id: &str,
    upload_root: &str,
    is_wss: bool,
    sessions: &SessionStore,
) -> Result<FileEntryResult, JsonRpcError>

Process a single FileEntry — resolve bytes, dedup, write to the upload root, and return a FileEntryResult.

upload_root is the directory under which a uploads/ subdir is created and bytes are written. Callers should pass the per-agent workspace dir, NOT the session cwd — uploads belong to the agent, not to whatever directory the user happened to launch the TUI from.