Rename Project and Replace Ray References with Distributed DataFusion (or New Name)

[NGA-TRAN]

The project is undergoing a naming transition. While some updates have already been made—such as using Distributed DataFusion in preliminary docs and build scripts—many code paths, identifiers, and references still use the outdated Ray-based naming (e.g., DFray...).

Some Tasks:

• Finalize the new project name (possibly Distributed DataFusion, or solicit input from the open-source community)
• Replace remaining Ray-inspired names across:
• Structs, modules, and function names (e.g., DFrayProcessor, dfray_proxy)
• Documentation, internal comments, CLI help messages
• Update CI/CD configs and any internal tooling scripts to reflect the new name
• Optionally tag a release before the rename for clean versioning history

This will align the project’s identity with its evolving architecture and remove legacy terminology for clarity.

[NGA-TRAN]

Done in #43