Add `run --interactive` (`-i`) which renders a split-screen
TUI inside the run command: scrollback output on top, input footer
on the bottom with prompt, permission, and question views.
This bridges the gap between headless `run` and the full TUI,
giving users an interactive experience without leaving the CLI
pipeline. Tool rendering, session data reduction, and stream
transport are extracted into run/ submodules to keep the
orchestration manageable.
*.shared.ts files contain shared logic for both run and the TUI, but
are intentionally kept in /run for now until later refactor
