fix(tools): add hint for project_not_found error

internal/tools/helpers.go

@@ -87,6 +87,7 @@ func resolveProject(ctx context.Context, db *store.DB, sessions *session.ActiveP
 					Type:    mcperrors.TypeProjectNotFound,
 					Field:   "project",
 					Project: projectRef,
+					Hint:    fmt.Sprintf("project %q does not exist yet; call create_project with name=%q first, then retry", projectRef, projectRef),
 				},
 			)
 		}