Implements a professional, standalone HTML export feature for Hermes sessions.
Key changes:
- Adds 'hermes sessions export <file>.html' support to the CLI.
- Implements a dark-mode-first, responsive HTML generator in 'hermes_cli/session_export_html.py'.
- Single session export features a focused, centered 90% width layout.
- Multi-session export adds a fixed sidebar with session switching and real-time search filtering.
- ZERO external dependencies; all styles and JS are embedded for offline portability.
