Introduce `ui.scrollback_lines` (default 2000) to cap the number of chat lines kept in memory, with `0` disabling trimming. Implement automatic trimming of older lines, maintain a scroll offset, and show a “↓ New messages (press G)” badge when new messages arrive off‑screen. Update core UI settings, TUI rendering, chat app state, migrations, documentation, and changelog to reflect the new feature.
- Introduce `ui.input_max_rows` (default 5) to control how many rows the input panel expands before scrolling.
- Bump `CONFIG_SCHEMA_VERSION` to **1.2.0** and update migration documentation.
- Update `configuration.md` and migration guide to describe the new setting.
- Adjust TUI height calculation to respect `input_max_rows` and add horizontal scrolling support for long lines.
- Add `unicode-segmentation` dependency for proper grapheme handling.
- Introduce `show_onboarding` UI setting (default true) and persist its state after first launch.
- Show onboarding status line and system status on initial run; fallback to normal status thereafter.
- Implement `show_tutorial` method displaying keybinding tips and system status.
- Register `:tutorial` command in command palette.
- Add migration documentation explaining `schema_version` update and deprecation of `agent.max_tool_calls`.
- Update README with description of the new tutorial command.
