test: add root command tests for complete coverage

Add TestRootCommand to match gmail-ro test coverage:
- Verifies command use, descriptions, version, and subcommands
- gro now has 69 test functions matching gmail-ro

Closes #7

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: rianjs

internal/cmd/root/root_test.go

@@ -0,0 +1,39 @@
+package root
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRootCommand(t *testing.T) {
+	t.Run("has correct use", func(t *testing.T) {
+		assert.Equal(t, "gro", rootCmd.Use)
+	})
+
+	t.Run("has short description", func(t *testing.T) {
+		assert.NotEmpty(t, rootCmd.Short)
+	})
+
+	t.Run("has long description", func(t *testing.T) {
+		assert.NotEmpty(t, rootCmd.Long)
+		assert.Contains(t, rootCmd.Long, "read-only")
+	})
+
+	t.Run("has version set", func(t *testing.T) {
+		assert.NotEmpty(t, rootCmd.Version)
+	})
+
+	t.Run("has subcommands", func(t *testing.T) {
+		subcommands := rootCmd.Commands()
+		assert.GreaterOrEqual(t, len(subcommands), 3)
+
+		var names []string
+		for _, sub := range subcommands {
+			names = append(names, sub.Name())
+		}
+		assert.Contains(t, names, "init")
+		assert.Contains(t, names, "config")
+		assert.Contains(t, names, "mail")
+	})
+}