- Add sanitize_for_prompt() function to security module
- Remove suspicious control characters (except whitespace)
- Detect and log common prompt injection patterns
- Escape dangerous XML-like tags used for prompt manipulation
- Truncate user content to max length (default 50000 chars)
- Integrate sanitization in parser before building LLM prompts
- Add comprehensive test suite (12 new tests)
Refs #338
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>