table: pass click modifiers through SelectRow event

[boboshan]

Fixes #2228

Summary

• Changes SelectRow(usize) to SelectRow(usize, Modifiers) to carry keyboard modifiers from the click event
• Adds set_selected_row_with_modifiers() alongside the existing set_selected_row() (which passes default modifiers)
• Enables consumers to implement Cmd+click / Shift+click multi-row selection without intercepting mouse events on the row div (which breaks on_drag on child elements)

AI Disclosure

This code was generated with AI assistance (Claude). The implementation has been manually tested in a production GPUI application with multi-row selection and native macOS drag.

[huacnlee]

Duplicate PR #2232?

[boboshan]

Not a duplicate of #2232. These are separate changes:

• This PR (table: pass click modifiers through SelectRow event #2231): Adds Modifiers to SelectRow event so consumers can implement multi-row selection (Cmd+click, Shift+click) without adding on_mouse_down to the row div (which breaks on_drag on child elements).

• menu: fix submenu dismiss propagation and ESC handling #2232: Auto-wires parent_menu on submenus built by the delegate's context_menu(). Different problem (submenu dismiss chain).

#2232 depends on this PR because both touch state.rs, but they solve different problems.

[boboshan]

Closing in favor of using GPUI's existing Window::modifiers() accessor.

Consumers of TableEvent::SelectRow can subscribe with cx.subscribe_in(&table_state, window, ...) to receive &mut Window in the closure, then call window.modifiers() to read the current modifier state at event-handling time. This delivers the same information for Cmd+click / Shift+click multi-selection without changing the event variant or TableDelegate API.

Verified locally — multi-row selection works as expected. Closing #2228 alongside.