Implement Break Mode Architecture - Core Distinguishing Feature

[toddysm]

Implement RegShape's core distinguishing feature - Break Mode - which allows deliberate mutation of HTTP requests to test registry implementations.

Acceptance Criteria

• Create libs/breakmode/ module structure
• Implement BreakModeConfig and BreakRule dataclasses
• Implement BreakModeMiddleware for transport layer
• Add built-in rule factories (wrong_digest, invalid_content_type, skip_auth, etc.)
• Wire CLI --break and --break-rules options
• Add break mode logging and file output
• Write comprehensive tests
• Update documentation

Files to Create/Modify

• src/regshape/libs/breakmode/__init__.py
• src/regshape/libs/breakmode/config.py
• src/regshape/libs/breakmode/rules.py
• src/regshape/libs/breakmode/middleware.py
• Update src/regshape/cli/main.py

References

• specs/architecture.md Section 5: Break Mode Architecture