feat: switch TUI from full-screen to inline viewport

[archon-instinct]

Summary

• Replace ratatui::init() (alternate-screen full-screen mode) with ratatui::init_with_options(TerminalOptions { viewport: Viewport::Inline(24) }) in src/main.rs
• The TUI now renders inline, directly below the invoked command, instead of taking over the full terminal
• Scrollback buffer and prior terminal output remain visible throughout the session

Changes

src/main.rs — one-line swap of the terminal init call:

• ratatui::init() → ratatui::init_with_options(ratatui::TerminalOptions { viewport: ratatui::Viewport::Inline(24) })
• Keyboard enhancement protocol setup/teardown is unchanged
• ratatui::restore() is unchanged and leaves the terminal clean

The inline height of 24 rows accommodates the most demanding screen (RenameForm, which has 13 fixed-height rows + a Fill(1) list), leaving 11 rows for the author list. All other screens are less constrained.

Verification

• src/tui/render.rs layouts use Constraint::Fill(1) throughout, so they adapt to the inline area without any layout changes
• Integration tests in tests/main_integration_test.rs test pre-TUI error paths (not-a-repo, not-a-TTY) and are unaffected by the viewport mode change
• ratatui::Viewport::Inline and ratatui::TerminalOptions are stable public API since ratatui 0.25; confirmed available in the locked ratatui 0.30.0

Fixes #7