fix(tui): suspend on ctrl+z

Bubble Tea's raw mode clears ISIG, so ctrl+z reached the TUI as a key and
was ignored instead of stopping the job. Return tea.Suspend for it on every
screen, and re-enable mouse tracking on resume, since Bubble Tea's restore
brings back the alt screen but not the mouse mode.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

strix/interface/tui/internal/app/model.go

@@ -384,7 +384,16 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			m.vulnerabilityCopyError = msg.err.Error()
 		}
 		return m, nil
+	case tea.ResumeMsg:
+		// Suspend turns mouse tracking off with the rest of the terminal state,
+		// but the restore brings back only the alt screen, so turn it back on.
+		return m, tea.EnableMouseCellMotion
 	case tea.KeyMsg:
+		// Raw mode clears ISIG, so ctrl+z arrives as a key instead of SIGTSTP.
+		// Suspend on every screen, the way a shell job would.
+		if msg.Type == tea.KeyCtrlZ {
+			return m, tea.Suspend
+		}
 		if m.showSplash {
 			switch msg.String() {
 			case "ctrl+c", "ctrl+q", "q", "esc":

strix/interface/tui/internal/app/model_test.go

@@ -1439,3 +1439,31 @@ func TestNarrowTerminalKeepsTheFrameIntact(t *testing.T) {
 		}
 	}
 }
+
+func TestCtrlZSuspendsFromEveryScreen(t *testing.T) {
+	for name, prepare := range map[string]func(*Model){
+		"splash": func(m *Model) { m.showSplash = true },
+		"modal":  func(m *Model) { m.showSplash = false; m.openModal(modalHelp) },
+		"main":   func(m *Model) { m.showSplash = false },
+	} {
+		model := New(nil)
+		prepare(&model)
+		_, cmd := model.Update(tea.KeyMsg{Type: tea.KeyCtrlZ})
+		if cmd == nil {
+			t.Fatalf("%s: ctrl+z returned no command", name)
+		}
+		if _, ok := cmd().(tea.SuspendMsg); !ok {
+			t.Fatalf("%s: ctrl+z did not suspend", name)
+		}
+	}
+}
+
+func TestResumeReenablesMouse(t *testing.T) {
+	_, cmd := New(nil).Update(tea.ResumeMsg{})
+	if cmd == nil {
+		t.Fatal("resume returned no command")
+	}
+	if msg := cmd(); msg != tea.EnableMouseCellMotion() {
+		t.Fatalf("resume did not re-enable mouse tracking: %#v", msg)
+	}
+}