fix broken query to get project fields

Author: tommaso-moro

pkg/github/projects.go

@@ -2,6 +2,7 @@ package github
 
 import (
 	"context"
+
 	"github.com/github/github-mcp-server/pkg/translations"
 	"github.com/go-viper/mapstructure/v2"
 	"github.com/mark3labs/mcp-go/mcp"
@@ -119,10 +120,12 @@ func GetProjectFields(getClient GetGQLClientFn, t translations.TranslationHelper
 					Project struct {
 						Fields struct {
 							Nodes []struct {
-								ID       githubv4.ID
-								Name     githubv4.String
-								DataType githubv4.String
-							}
+								ProjectV2Field struct {
+									ID       githubv4.ID
+									Name     githubv4.String
+									DataType githubv4.String
+								} `graphql:"... on ProjectV2Field"`
+							} 
 						} `graphql:"fields(first: 100)"`
 					} `graphql:"projectV2(number: $number)"`
 				} `graphql:"organization(login: $login)"`