feat: add interactive show & tell demo for Conversation Guardian

- 7 scenarios: benign, escalation, offensive, feedback loop, Irregular Labs, evasion, transcript
- Interactive menu with colored terminal output (ASCII-safe for Windows)
- Demonstrates full detection pipeline with real-time scoring
- Reproduces Irregular Labs paper attack scenario -> quarantine in 3 turns
- Shows transcript audit with SHA-256 content hashing and filtered views
- Fix unicode arrow in guardian logger for Windows compatibility

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: imran-siddique