oxfmt: walk and format at the same time, instead of walk, collect paths then format

[leaysgur]

• walk.rs
  • Before: Collected all file paths into memory before processing
  • After: Sends each discovered path immediately through a channel
• format.rs
  • Before: Wait for complete path collection, then start formatting
  • After: Two concurrent threads - one walks directories and sends paths, another receives and processes them
• service.rs
  • Before: Batch processing of all files at once
  • After: Added method to process individual files as they arrive