Function compute_updates_modal_scroll_for_selection 

pub fn compute_updates_modal_scroll_for_selection(
    entry_line_starts: &[u16],
    total_lines: u16,
    content_rect: Option<(u16, u16, u16, u16)>,
    selected: usize,
    total_items: usize,
    current_scroll: u16,
) -> u16

What: Compute updates-modal scroll offset that keeps the selected entry visible.

Inputs:

• entry_line_starts: Mapping from entry index to first rendered line in wrapped output.
• total_lines: Total rendered line count across wrapped updates rows.
• content_rect: Optional updates content rectangle tuple (x, y, width, height).
• selected: Selected entry index.
• total_items: Number of entries in the updates list.
• current_scroll: Existing scroll offset before adjustment.

Output:

• Returns the next clamped scroll offset as u16.

Details:

• Derives visible_lines from content_rect height and falls back to 1 when absent.
• Uses rendered-line mapping to support wrapped rows consistently.
• Clamps output to valid range to prevent underflow/overscroll.