refactor: extract coerce and stressorToString into util.js

static/exporter.js

@@ -1,5 +1,4 @@
-// RFC-compliant YAML serializer for Sompyler instrument blocks.
-// Operates on the model produced by ast-parser.js buildModel().
+import { stressorToString } from './util.js';
 
 // ── Shape ──────────────────────────────────────────────────────────────────
 // RFC §1.3.4.5: SHAPE = [PREFIX (":" / ";")] Node 1*(";" Node)
@@ -241,10 +240,6 @@ function patchInstrumentHeader(text, instruments) {
     return result.join('\n');
 }
 
-export function stressorToString(s) {
-    if (!s?.groups?.length) return '';
-    return s.groups.map(g => g.join(',')).join(';');
-}
 
 function patchBarMeta(doc, bar) {
     const props = [];