feat(tui): adopt an asynchronous Tokio runtime for the TUI frontend

Refactor TUI event handling and rendering to improve responsiveness and use a unified managed client worker.

crates/irtt-app/src/cmd/tui/ui.rs

@@ -106,7 +106,6 @@ pub(super) struct TuiState {
     details_open: bool,
     details_scroll: (u16, u16),
     pub(super) paused: bool,
-    pub(super) quit_requested: bool,
 }
 
 impl TuiState {
@@ -143,7 +142,6 @@ impl TuiState {
             details_open: false,
             details_scroll: (0, 0),
             paused: false,
-            quit_requested: false,
         }
     }
 
@@ -939,10 +937,6 @@ pub(super) fn draw_dashboard(frame: &mut Frame<'_>, state: &TuiState) {
     frame.render_widget(status_line(state), rows[3]);
 }
 
-pub(super) fn should_render(now: Instant, next_render: Instant, paused: bool, force: bool) -> bool {
-    force || (!paused && now >= next_render)
-}
-
 fn dashboard_layout(area: Rect, state: &TuiState) -> [Rect; 4] {
     let footer = 3 + u16::from(state.last_warning.is_some());
     let target_rows = state.targets.len().min(6) as u16;