New primary guide at `user-guide/tui.md` covering launch, requirements,
keybindings, slash commands, status line, configuration, sessions, and
the revert path. Matches the voice of `user-guide/cli.md`.
Cross-links:
- `user-guide/cli.md`: tip callout pointing readers at the Ink TUI
- `getting-started/quickstart.md`: shows both `hermes` and `hermes --tui`
under "Start Chatting" so first-run users know they have the choice
- `reference/environment-variables.md`: new "Interface" section with
`HERMES_TUI` and `HERMES_TUI_DIR`
- `reference/cli-commands.md`: `--tui` and `--dev` added to global options
Sidebar: `user-guide/tui` slotted right after `user-guide/cli`.
2812bfe5b9