Deny instead of crashing when a control permission check throws (#1033)

A permission function runs during ingress permission checking, before
the request body is validated. UserBulkImportRequest.permission read the
raw, unvalidated message.data and threw a bare Error for an unknown
importType. That error is not a PermissionError, so _processMessage
rethrew it to the connector "message" listener, which emitted "error" on
the connector. Controller-side connectors have no "error" listener, so
Node rethrew and handleUnhandledErrors exited the process.

Repro: a control client with client-side validateSent disabled sends
UserBulkImportRequest with importType "foo"; the client gets a normal
RequestError response and the controller then logs a fatal uncaught
exception and exits.

Fix both layers: _processMessage now logs and drops an unexpected error
from the permission check (control connections only, where a response
was already sent) instead of rethrowing, and UserBulkImportRequest
throws a PermissionError for an unknown importType so it is denied
cleanly. A genuine PermissionError still denies silently as before.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

test/lib/data/messages_user.test.js

@@ -0,0 +1,27 @@
+import assert from "node:assert/strict";
+import * as lib from "@clusterio/lib";
+
+describe("lib/data/messages_user", function() {
+	describe("UserBulkImportRequest", function() {
+		// A user that grants every permission, so only the importType switch
+		// can reject the request.
+		function grantAllUser() {
+			const checked = [];
+			return { checked, checkPermission(permission) { checked.push(permission); } };
+		}
+
+		it("should deny an unknown importType with a PermissionError", function() {
+			const user = grantAllUser();
+			assert.throws(
+				() => lib.UserBulkImportRequest.permission(user, { data: { importType: "foo", users: [] } }),
+				lib.PermissionError,
+			);
+		});
+
+		it("should check permissions for a known importType", function() {
+			const user = grantAllUser();
+			lib.UserBulkImportRequest.permission(user, { data: { importType: "admins", users: [] } });
+			assert.deepEqual(user.checked, ["core.user.bulk_import", "core.user.set_admin"]);
+		});
+	});
+});