Add AddFlags() and Validate() methods to outputOptions

Add architecture methods to outputOptions to follow the established
pattern used by other option sets in the codebase (branchOptions,
verifierOptions, etc.).

- Add AddFlags() method to initialize format and register the --format flag
- Add Validate() method to verify format is either 'text' or 'json'
- Add test coverage for Validate() method with valid and invalid inputs
- Import cobra package for AddFlags() implementation

This prepares outputOptions to be properly integrated into embedding
option sets following the command architecture pattern.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>
Signed-off-by: Ralph Bean <[email protected]>

Author: ralphbean

internal/cmd/output.go

@@ -8,6 +8,8 @@ import (
 	"fmt"
 	"io"
 	"os"
+
+	"github.com/spf13/cobra"
 )
 
 const (
@@ -20,6 +22,20 @@ type outputOptions struct {
 	format string
 }
 
+// AddFlags adds output-related flags to the command
+func (oo *outputOptions) AddFlags(cmd *cobra.Command) {
+	oo.format = OutputFormatText
+	cmd.PersistentFlags().StringVar(&oo.format, "format", OutputFormatText, "Output format: 'text' (default) or 'json'")
+}
+
+// Validate checks that the output format is valid
+func (oo *outputOptions) Validate() error {
+	if oo.format != OutputFormatText && oo.format != OutputFormatJSON {
+		return fmt.Errorf("output format must be 'text' or 'json', got: %s", oo.format)
+	}
+	return nil
+}
+
 // getWriter returns the writer to use for output (currently always os.Stdout)
 func (oo *outputOptions) getWriter() io.Writer {
 	return os.Stdout

internal/cmd/verifycommit_test.go

@@ -136,3 +136,37 @@ func TestOutputOptions_OutputFormatIsJSON(t *testing.T) {
 		})
 	}
 }
+
+func TestOutputOptions_Validate(t *testing.T) {
+	tests := []struct {
+		name    string
+		format  string
+		wantErr bool
+	}{
+		{
+			name:    "valid text format",
+			format:  OutputFormatText,
+			wantErr: false,
+		},
+		{
+			name:    "valid JSON format",
+			format:  OutputFormatJSON,
+			wantErr: false,
+		},
+		{
+			name:    "invalid format",
+			format:  "invalid",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			opts := outputOptions{format: tt.format}
+			err := opts.Validate()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Validate() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}