Adds machine-readable output format for driving nt-flash from other
tools like NT Helper. Output format:

  STATUS:<STAGE>:<PERCENT>:<MESSAGE>
  PROGRESS:<STAGE>:<PERCENT>:<MESSAGE>
  ERROR:<MESSAGE>

Includes MACHINE.md documenting the output format for LLM consumption.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>