feat: Improved the UI for the CLI interface

[PrasanthYT]

Overview

This PR introduces a full interactive Terminal UI (TUI) mode for Scanr and refactors the CLI startup behavior to support a dashboard-first experience.

Scanr now launches into an interactive interface by default, shifting from command-first execution to an operational workflow model.

This enhances usability while preserving core functionality and CI compatibility.

Startup Behavior Changes

Previous Behavior

• scanr auto-triggered scan execution.

New Behavior

• scanr launches TUI immediately in empty state.
• Ctrl + S starts scan in background.
• Loader spinner displayed during active scan.
• Clear visual status feedback in header.

This improves UX while maintaining deterministic behavior.

New TUI Module

Added

• tui.rs

Responsibilities

• Alternate screen lifecycle management
• Raw mode handling
• Event loop management (30 FPS)
• Keyboard input handling
• Rendering pipeline
• Popup management
• Graceful cleanup on exit

Terminal state is restored cleanly after exit.

CLI Wiring Update

Modified

• main.rs

Changes:

• Command argument made optional
• scanr (no subcommand) launches TUI
• None branch invokes:

tui::run_tui(PathBuf::from("."));

This keeps CLI and interactive mode unified.

Visual Cleanup & UX Improvements

Refined layout to reduce congestion and improve readability:

• Narrowed left panel width

• Shortened header hint text

• Removed focus noise in header

• Simplified panel titles

• Reduced table column widths and labels:

  • Sev
  • Vuln
  • Target
  • Break

• Cleaner empty-state messaging

Improves clarity and reduces visual overload.

Dependency Updates

Updated Cargo.toml:

• Added:

  • ratatui
  • crossterm

These power rendering and terminal interaction.

Preserved Core Behavior

All existing functionality remains intact:

• Overview / Dependencies / Recommendations views
• Arrow navigation
• Enter → detail popup
• Esc → back
• q → quit
• 30 FPS event loop
• Resize handling
• Clean terminal restore

No regression in core logic.

Impact

• Improves interactive usability
• Enhances developer workflow experience
• Maintains CI compatibility
• Preserves JSON/SARIF modes
• No breaking changes to existing flags

Validation

• Manual navigation tested
• Background scan behavior verified
• Terminal state restored correctly on exit
• cargo build --workspace --release passes
• No panic during lifecycle transitions

Why This Matters

This change transitions Scanr from:

Command execution tool

To:

Interactive operational security dashboard.

It improves real-world usability without sacrificing automation readiness.