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.

Cargo.lock

@@ -317,6 +317,7 @@ dependencies = [
  "crossterm_winapi",
  "derive_more",
  "document-features",
+ "futures-core",
  "mio",
  "parking_lot",
  "rustix",
@@ -753,10 +754,12 @@ dependencies = [
  "clap",
  "crossterm",
  "ctrlc",
+ "futures-core",
  "irtt-client",
  "irtt-proto",
  "irtt-server",
  "irtt-stats",
+ "nix 0.31.3",
  "ratatui",
  "tokio",
 ]