fix: terminal hangs, right arrow blocking, and runaway iris processes (#142)

closes #137

- right arrow consumed the escape sequence without forwarding it, so the
cursor couldn't move back right after moving left (60149a2)
- p10k's instant prompt redirects stdout to a temp file that exec iris
inherits, sending the overlay there instead of the terminal and looking
like a dead keyboard. Reopens /dev/tty when stdout isn't a terminal
(7ebbb0c)
- zsh/bash autostart lacked the interactivity check fish already had, so
agentic tools sourcing your rc file spawned a rogue iris that seized
/dev/tty (5fe58be)

root/init_test.go

@@ -0,0 +1,59 @@
+package root
+
+import (
+	"io"
+	"os"
+	"strings"
+	"testing"
+)
+
+func captureInitScript(t *testing.T, shell string) string {
+	t.Helper()
+
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	original := os.Stdout
+	os.Stdout = w
+	initCmd.Run(initCmd, []string{shell})
+	_ = w.Close()
+	os.Stdout = original
+
+	out, err := io.ReadAll(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(out)
+}
+
+// a tool runner that sources the rc file in a non-interactive shell must not
+// exec a second iris, which would seize the tty from the one already running
+func TestInitAutostartRequiresInteractiveShell(t *testing.T) {
+	guards := map[string]string{
+		"zsh":  "[[ -o interactive ]]",
+		"bash": "[[ $- == *i* ]]",
+		"fish": "status is-interactive",
+	}
+
+	for shell, guard := range guards {
+		t.Run(shell, func(t *testing.T) {
+			script := captureInitScript(t, shell)
+
+			head, _, found := strings.Cut(script, "exec iris")
+			if !found {
+				t.Fatalf("%s init script has no autostart", shell)
+			}
+
+			cond := strings.LastIndex(head, "\nif ")
+			if cond < 0 {
+				t.Fatalf("%s autostart is not inside an if", shell)
+			}
+
+			if !strings.Contains(head[cond:], guard) {
+				t.Fatalf("%s autostart is not guarded by %q:\n%s", shell, guard, head[cond:])
+			}
+		})
+	}
+}