fix: address Plan 2 final-review findings

- tui/doc.go: remove teatest blank import (test harness in prod binary)
- cmd: honor wizard HaltOnError toggle in addition to --halt-on-error flag
- cmd: wire SIGINT/SIGTERM to root context via signal.NotifyContext
- dashboard/run: derive engine context and cancel on tea.Program exit
  so the engine goroutine does not outlive Run

cmd/archduino/main.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"os/signal"
+	"syscall"
 	"time"
 
 	"github.com/spf13/cobra"
@@ -41,7 +43,13 @@ func main() {
 		Version:       version,
 	}
 	root.AddCommand(newInstallCmd())
-	if err := root.Execute(); err != nil {
+
+	// Wire SIGINT/SIGTERM to a cancellable context so long-running phases
+	// (engine.Run, sudo keepalive) observe the cancellation promptly.
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+
+	if err := root.ExecuteContext(ctx); err != nil {
 		fmt.Fprintln(os.Stderr, "error:", err)
 		os.Exit(1)
 	}
@@ -140,7 +148,8 @@ func newInstallCmd() *cobra.Command {
 					fmt.Fprintln(os.Stdout, "installation cancelled")
 					return nil
 				}
-				sum, runErr = dashboard.Run(ctx, Registry, finalState, halt)
+				// Either the CLI flag or the wizard toggle can force halt-on-error.
+				sum, runErr = dashboard.Run(ctx, Registry, finalState, halt || finalState.HaltOnError)
 			}
 
 			ended := time.Now().UTC()

internal/tui/dashboard/run.go

@@ -23,10 +23,18 @@ func Run(ctx context.Context, reg *module.Registry, state tui.WizardState, halt
 	m := NewModel(selected, nameByID)
 	p := tea.NewProgram(m, tea.WithContext(ctx))
 
+	// Derived context so that when p.Run() returns (user pressed q, tea
+	// errored, parent ctx cancelled) the engine goroutine is cancelled
+	// too. Deferred cancel ensures no orphan goroutine outlives Run.
+	engineCtx, cancelEngine := context.WithCancel(ctx)
+	defer cancelEngine()
+
 	reporter := tui.NewTeaReporter(p)
 
 	go func() {
-		summary, err := engine.Run(ctx, reg, engine.RunOptions{
+		// TODO(plan-3): forward state.Parallelism once engine.RunOptions
+		// gains a Parallelism field and the engine supports concurrent Apply.
+		summary, err := engine.Run(engineCtx, reg, engine.RunOptions{
 			Selected:    selected,
 			HaltOnError: halt,
 			Reporter:    reporter,

internal/tui/doc.go

@@ -2,10 +2,3 @@
 // that collects user choices and the Bubble Tea dashboard that renders
 // live module status during engine.Run.
 package tui
-
-import (
-	_ "github.com/charmbracelet/bubbletea"
-	_ "github.com/charmbracelet/huh"
-	_ "github.com/charmbracelet/lipgloss"
-	_ "github.com/charmbracelet/x/exp/teatest"
-)