Unwrap scalars in shell output mode. (#2548)

* feat: Add UnwrapScalar to ShellVariablesPreferences

- Add UnwrapScalar boolean field to ShellVariablesPreferences struct.
- Initialize UnwrapScalar to false in NewDefaultShellVariablesPreferences.
- This preference will control whether shell output should be quoted or raw.

* feat: Propagate unwrapScalar to ShellVariablesPreferences

- In configureEncoder function, set UnwrapScalar in ConfiguredShellVariablesPreferences.
- This ensures the -r flag's state is passed to the shell encoder for raw output control.

* feat: Implement conditional quoting in shellVariablesEncoder

- Modify doEncode method to check pe.prefs.UnwrapScalar.
- If UnwrapScalar is true, output raw node.Value.
- Otherwise, use quoteValue for shell-safe quoting.
- This enables quote-free output for Kubernetes workflows when -r is used.

* test: Add tests for UnwrapScalar in shell encoder

- Introduce assertEncodesToUnwrapped helper function.
- Add TestShellVariablesEncoderUnwrapScalar to verify quote-free output with -r.
- Add TestShellVariablesEncoderDefaultQuoting to confirm default quoting behavior without -r.
- Ensure comprehensive testing of conditional quoting logic for shell output.

* remove redundant test

pkg/yqlib/encoder_shellvariables_test.go

@@ -135,3 +135,36 @@ func TestShellVariablesEncoderCustomSeparatorArray(t *testing.T) {
 func TestShellVariablesEncoderCustomSeparatorSingleChar(t *testing.T) {
 	assertEncodesToWithSeparator(t, "a:\n b: value", "aXb=value", "X")
 }
+
+func assertEncodesToUnwrapped(t *testing.T, yaml string, shellvars string) {
+	var output bytes.Buffer
+	writer := bufio.NewWriter(&output)
+
+	originalUnwrapScalar := ConfiguredShellVariablesPreferences.UnwrapScalar
+	defer func() {
+		ConfiguredShellVariablesPreferences.UnwrapScalar = originalUnwrapScalar
+	}()
+
+	ConfiguredShellVariablesPreferences.UnwrapScalar = true
+
+	var encoder = NewShellVariablesEncoder()
+	inputs, err := readDocuments(strings.NewReader(yaml), "test.yml", 0, NewYamlDecoder(ConfiguredYamlPreferences))
+	if err != nil {
+		panic(err)
+	}
+	node := inputs.Front().Value.(*CandidateNode)
+	err = encoder.Encode(writer, node)
+	if err != nil {
+		panic(err)
+	}
+	writer.Flush()
+
+	test.AssertResult(t, shellvars, strings.TrimSuffix(output.String(), "\n"))
+}
+
+func TestShellVariablesEncoderUnwrapScalar(t *testing.T) {
+	assertEncodesToUnwrapped(t, "a: Lewis Carroll", "a=Lewis Carroll")
+	assertEncodesToUnwrapped(t, "b: 123", "b=123")
+	assertEncodesToUnwrapped(t, "c: true", "c=true")
+	assertEncodesToUnwrapped(t, "d: value with spaces", "d=value with spaces")
+}