Fix: guard load_plugins() so helper files without a default export don't crash tool init

selection_actions.js uses named exports only (no default export).
load_plugins() was calling new classObj.default(ctx) on every file in tools/,
causing TypeError which aborted render_main_tools() -> render_main_gui() ->
leaving menu and toolbar blank. Added null guard and per-file try/catch,
matching the defensive pattern already added to load_modules().

https://claude.ai/code/session_01WVDg7amsy1TTtxvpku7bcM

frontend/src/js/core/gui/gui-tools.js

@@ -46,7 +46,9 @@ class GUI_tools_class {
 					moduleKey = parts[parts.length - 1];
 				}
 
+				try {
 					var classObj = plugins_context(key);
+					if (!classObj.default) return; // skip helper files without a default export
 					var object = new classObj.default(ctx);
 
 					var title = _this.Helper.ucfirst(object.name);
@@ -64,6 +66,9 @@ class GUI_tools_class {
 					if(typeof object.load != "undefined") {
 						object.load();
 					}
+				} catch(e) {
+					console.error('[load_plugins] Failed to load ' + key + ':', e);
+				}
 			}
 		});
 	}