table: pass click modifiers through SelectRow event

[boboshan]

Problem

TableEvent::SelectRow(usize) doesn't carry the keyboard modifiers from the click event. This makes it impossible to implement Cmd+click / Shift+click multi-row selection without adding on_mouse_down handlers to the row div, which breaks on_drag on child elements (GPUI's drag detection uses pending_mouse_down which conflicts).

Solution

Change SelectRow(usize) to SelectRow(usize, Modifiers) and pass e.modifiers() from the ClickEvent in on_row_left_click. Keyboard navigation (arrow keys) passes Modifiers::default() via the existing set_selected_row().

pub enum TableEvent {
    SelectRow(usize, gpui::Modifiers),  // was: SelectRow(usize)
    // ...
}

Adds set_selected_row_with_modifiers() alongside the existing set_selected_row() for backward compatibility.

Branch: boboshan/feat/select-row-modifiers