Add comprehensive in-app help and rewrite README
In-app documentation (Settings → Help):
- Navigable two-column layout with sidebar sections
- Getting Started guide for creating first connection
- SSH, Telnet, RAW TCP, and GitHub connection guides
- Sessions & Tabs (split panes, recording, tab management)
- Security & Credentials (vault, keychain, known hosts explained)
- Full keyboard shortcuts reference table
- Import & Export guide (encrypted .nexus, OpenSSH config)
- Troubleshooting section (common issues and fixes)
- Fun Things to Try (Star Wars ASCII, MapSCII, BBS, GitHub SSH test)
All documentation in British English, written for average users.
README.md fully rewritten to reflect current feature set — removed
all outdated 'planned'/'in progress' items, updated architecture,
added troubleshooting, corrected encryption parameters.
andy
8a9c17046d