/domain-guidance

Deep dive guidance on CMMC v2.0 domains and practices

# CMMC Domain Guidance

Provides detailed implementation guidance for CMMC v2.0 domains and their associated practices.

## Arguments
- `$1` - Domain abbreviation (required: AC, AM, AU, AT, CM, IA, IR, MA, MP, PS, PE, RE, RM, CA, SA, SC, SI)
- `$2` - CMMC level (optional: 1, 2, 3 - shows practices for that level)

## 14 CMMC Domains

### Access Control (AC) - 22 practices
Controls who can access systems and data based on approved authorizations.

**Key practices**:
- AC.L1-3.1.1: Limit access to authorized users
- AC.L1-3.1.2: Limit access to transaction types
- AC.L2-3.1.20: External conne...