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/ui/exit_test.go

@@ -0,0 +1,81 @@
+package ui
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// fakeChildExit satisfies the transparentExit interface, standing in for
+// *runner.ChildExitError without a cross-package import.
+type fakeChildExit struct {
+	code     int
+	signaled bool
+	pmName   string
+}
+
+func (e *fakeChildExit) Error() string    { return fmt.Sprintf("%s exited with code %d", e.pmName, e.code) }
+func (e *fakeChildExit) ExitCode() int    { return e.code }
+func (e *fakeChildExit) Transparent() bool { return true }
+func (e *fakeChildExit) IsSignaled() bool { return e.signaled }
+
+func withVerbosity(t *testing.T, level VerbosityLevel) {
+	t.Helper()
+	prev := verbosityLevel
+	verbosityLevel = level
+	t.Cleanup(func() { verbosityLevel = prev })
+}
+
+func TestClassifyExit(t *testing.T) {
+	t.Run("genuine non-zero child exit prints a dim notice and mirrors the code", func(t *testing.T) {
+		withVerbosity(t, VerbosityLevelNormal)
+
+		d := classifyExit(&fakeChildExit{code: 1, pmName: "npm"})
+
+		assert.True(t, d.transparent)
+		assert.Equal(t, 1, d.code)
+		assert.True(t, d.notice)
+		assert.Equal(t, "↳ pmg: npm exited with code 1", d.message)
+	})
+
+	t.Run("transparent exit is detected even when wrapped", func(t *testing.T) {
+		withVerbosity(t, VerbosityLevelNormal)
+
+		wrapped := fmt.Errorf("failed to execute command: %w", &fakeChildExit{code: 2, pmName: "pnpm"})
+		d := classifyExit(wrapped)
+
+		assert.True(t, d.transparent)
+		assert.Equal(t, 2, d.code)
+		assert.True(t, d.notice)
+	})
+
+	t.Run("signal termination is silent but still mirrors the code", func(t *testing.T) {
+		withVerbosity(t, VerbosityLevelNormal)
+
+		d := classifyExit(&fakeChildExit{code: 130, signaled: true, pmName: "npm"})
+
+		assert.True(t, d.transparent)
+		assert.Equal(t, 130, d.code)
+		assert.False(t, d.notice)
+		assert.Empty(t, d.message)
+	})
+
+	t.Run("silent mode suppresses the notice", func(t *testing.T) {
+		withVerbosity(t, VerbosityLevelSilent)
+
+		d := classifyExit(&fakeChildExit{code: 1, pmName: "npm"})
+
+		assert.True(t, d.transparent)
+		assert.Equal(t, 1, d.code)
+		assert.False(t, d.notice)
+	})
+
+	t.Run("non-transparent error falls through to the loud path", func(t *testing.T) {
+		d := classifyExit(errors.New("some PMG failure"))
+
+		assert.False(t, d.transparent)
+		assert.False(t, d.notice)
+	})
+}