fix: Suppress non-PMG error from Critical UI Error (#311)

* fix: Suppress non-PMG error from Critical UI Error

* fix: Code review fixes

---------

Co-authored-by: Sahil Bansal <bansalsahil315@gmail.com>

internal/pty/exiterror_test.go

@@ -0,0 +1,34 @@
+//go:build !windows
+
+package pty
+
+import (
+	"errors"
+	"syscall"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewExitError(t *testing.T) {
+	underlying := errors.New("boom")
+
+	t.Run("normal non-zero exit carries the raw code", func(t *testing.T) {
+		e := newExitError(2, syscall.WaitStatus(2<<8), underlying)
+		assert.Equal(t, 2, e.Code)
+		assert.False(t, e.Signaled)
+		assert.ErrorIs(t, e, underlying)
+	})
+
+	t.Run("signal termination resolves to 128+signum and marks signaled", func(t *testing.T) {
+		e := newExitError(-1, syscall.WaitStatus(int(syscall.SIGINT)), underlying)
+		assert.Equal(t, 128+int(syscall.SIGINT), e.Code)
+		assert.True(t, e.Signaled)
+	})
+
+	t.Run("no wait status falls back to the provided code", func(t *testing.T) {
+		e := newExitError(-1, nil, underlying)
+		assert.Equal(t, -1, e.Code)
+		assert.False(t, e.Signaled)
+	})
+}