Modernize the interactive TUI

## Goal

Modernize Pentect's interactive terminal UI.

## Current state

This issue currently does not define which commands or screens should change, the intended interaction model, or measurable acceptance criteria. Implementing it as written would require guessing at product behavior.

## Definition work required

- Identify the existing TUI flows that need improvement.
- Specify navigation, keyboard behavior, loading/error states, and non-interactive fallbacks.
- Provide target screenshots or wireframes.
- Define accessibility and terminal compatibility requirements.
- Split implementation into independently testable issues before development.

This remains a P3 design and product-definition task until those decisions are documented.

Start by inventorying the existing interactive TUI flows and documenting which commands or screens need improvement. Define navigation, keyboard behavior, loading and error states, non-interactive fallbacks, accessibility, terminal compatibility, and target screenshots or wireframes. Once those decisions are recorded, split the work into independently testable implementation issues.

Written by the indexing model from the issue text.