v1.2.1: fix tracker_add in executor + labelCls + descr context + script order

Opus review fixes:
- executor.py: tracker_add inside executor after instance_uid, before params/run (A3, orphan protection)
- executor.py: descr parameter (version/context instead of hardcoded)
- api_test.py: pass client_id/stand/descr, remove duplicate tracker_add
- scenario.py: pass client_id/stand/descr with scenario context
- params-render.js: fix labelCls ReferenceError in renderMapFixedRow (pre-existing bug)
- index.html: params-render.js already before operations.js (verified)

site/static/js/params-render.js

@@ -31,6 +31,7 @@ function renderParamRow(p, allInst) {
 
 function renderMapFixedRow(p, dfl) {
     const dd = p.dataDescriptor;
+    const labelCls = p.isRequired ? (dfl ? 'req' : 'req-nodfl') : '';
     let subHtml = '';
     let dflObj = {};
     try { dflObj = JSON.parse(dfl || '{}'); } catch (e) { }