feat: add scrollable and compact TUI for status board and validation views

[l50]

Key Changes:

• Introduced vertical scrolling and keyboard navigation to the status board TUI
• Implemented compact mode for both status board and validation views to fit small terminal panes
• Improved user experience with pinned headers/footers and adaptive keyboard hints
• Refactored TUI logic for better separation of concerns and maintainability

Added:

• Vertical scroll support and keyboard navigation (j/k, PgUp/PgDn, g/G) in the status board TUI with pinned headers and footers
• Compact rendering mode for both the status board and validation views, which automatically activates when the content exceeds available terminal height, removing blank spacer lines and minimizing hints for better fit

Changed:

• Status board TUI exit behavior now prints a final static snapshot to stdout after quitting, ensuring the last frame is visible in terminal scrollback (especially useful in tmux)
• Refactored key handling and poll update logic in the status board TUI into dedicated methods for clarity and extensibility
• Validation view layout now conditionally omits spacers and keyboard hints in compact mode for improved usability in small terminal splits
• Updated summary panel rendering logic in the validate command to always display the summary, regardless of TUI usage

Removed:

• Conditional logic that previously suppressed summary panel output when TUI was not used in the validate command, ensuring consistent summary reporting