Use typed IconTheme constants from Go SDK

Replace string conversions with mcp.IconThemeLight and mcp.IconThemeDark
constants to match the SDK's typed IconTheme field. This fixes the CI build
errors where string literals were being used instead of the proper IconTheme type.

Co-authored-by: SamMorrowDrums <4811358+SamMorrowDrums@users.noreply.github.com>

Author: Copilot

pkg/octicons/octicons.go

@@ -73,12 +73,12 @@ func Icons(name string) []mcp.Icon {
 		{
 			Source:   DataURI(name, ThemeLight),
 			MIMEType: "image/png",
-			Theme:    string(ThemeLight),
+			Theme:    mcp.IconThemeLight,
 		},
 		{
 			Source:   DataURI(name, ThemeDark),
 			MIMEType: "image/png",
-			Theme:    string(ThemeDark),
+			Theme:    mcp.IconThemeDark,
 		},
 	}
 }

pkg/octicons/octicons_test.go

@@ -4,6 +4,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/modelcontextprotocol/go-sdk/mcp"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -87,13 +88,13 @@ func TestIcons(t *testing.T) {
 			assert.Equal(t, DataURI(tc.icon, ThemeLight), result[0].Source)
 			assert.Equal(t, "image/png", result[0].MIMEType)
 			assert.Empty(t, result[0].Sizes) // Sizes field omitted for backward compatibility
-			assert.Equal(t, "light", result[0].Theme)
+			assert.Equal(t, mcp.IconThemeLight, result[0].Theme)
 
 			// Verify second icon is dark theme
 			assert.Equal(t, DataURI(tc.icon, ThemeDark), result[1].Source)
 			assert.Equal(t, "image/png", result[1].MIMEType)
 			assert.Empty(t, result[1].Sizes) // Sizes field omitted for backward compatibility
-			assert.Equal(t, "dark", result[1].Theme)
+			assert.Equal(t, mcp.IconThemeDark, result[1].Theme)
 		})
 	}
 }