feat: Add embodi CLI + fix macOS + clean README

[dddimcha]

Changes

1. New embodi CLI tool

Single entry point for all operations:

./embodi build              # Build kernel
./embodi build --debug      # Debug build
./embodi iso                # Create ISO
./embodi iso --model X.gguf # ISO with embedded model
./embodi run                # Run in QEMU
./embodi run --memory 2G    # With more RAM
./embodi clean              # Clean build
./embodi test               # Run tests

2. Fix macOS grep compatibility

Replace grep -P with portable awk in create_iso.sh

3. Clean README

• Removed emojis
• Clear CLI reference
• Step-by-step instructions
• Professional formatting