Add dedicated workflow for documentation deployment

[MaxGhenis]

Summary

This PR adds a separate GitHub Actions workflow specifically for deploying documentation, which avoids the need to run the full test suite for documentation-only changes.

Problem

Currently, documentation deployment requires running the full test suite including dataset builds, which:

• Takes a long time (often 30+ minutes)
• Uses significant CI resources
• Creates unnecessary delays for documentation updates

Solution

Added a new deploy_docs.yaml workflow that:

• Triggers on pushes to main that modify files in docs/
• Can be manually triggered via workflow_dispatch
• Only builds and deploys documentation without running tests
• Significantly reduces deployment time for documentation changes

Benefits

• ⚡ Faster documentation updates (minutes instead of 30+ minutes)
• 💰 Reduced CI resource usage
• 🔄 Better developer experience for documentation contributors
• ✅ Still maintains full testing for code changes via existing workflows

The existing code_changes.yaml workflow remains unchanged and will still deploy docs after code changes with full testing.

[MaxGhenis]

Closing - documentation deployment already exists in the main test workflow after tests pass. Keeping single deployment path for clarity.