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]>

Makefile

@@ -1,4 +1,4 @@
-.PHONY: help install dev-install format lint type-check security check-all clean pre-commit setup-dev dev viewer wheel tui-build tui-test tui-lint
+.PHONY: help install dev-install format lint format-check lint-check type-check security check-all clean pre-commit setup-dev dev viewer wheel tui-build tui-test tui-lint
 
 TUI_BINARY := build/sidecar/strix-tui$(if $(filter Windows_NT,$(OS)),.exe)
 
@@ -10,7 +10,9 @@ help:
 	@echo ""
 	@echo "Code Quality:"
 	@echo "  format        - Format code with ruff"
-	@echo "  lint          - Lint code with ruff"
+	@echo "  lint          - Lint code with ruff and apply fixes"
+	@echo "  format-check  - Check formatting without modifying files"
+	@echo "  lint-check    - Check lint without modifying files"
 	@echo "  type-check    - Run type checking with mypy and pyright"
 	@echo "  security      - Run security checks with bandit"
 	@echo "  check-all     - Run all code quality checks"
@@ -45,6 +47,12 @@ lint:
 	uv run ruff check . --fix
 	@echo "✅ Linting complete!"
 
+format-check:
+	uv run ruff format --check .
+
+lint-check:
+	uv run ruff check .
+
 type-check:
 	@echo "🔍 Type checking with mypy..."
 	uv run mypy strix/
@@ -57,7 +65,7 @@ security:
 	uv run bandit -r strix/ -c pyproject.toml
 	@echo "✅ Security checks complete!"
 
-check-all: format lint type-check security
+check-all: format-check lint-check type-check security
 	@echo "✅ All code quality checks passed!"
 
 pre-commit:

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)
+	}
+}