chore(sales-invoice): clarify tax-article comments (drop stale TEST/mirror notes)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

jey_erp/custom/sales_invoice_tax_articles.py

@@ -43,7 +43,7 @@ def sync_item_tax_articles(doc, method=None):
     ]
     doc.custom_item_tax_articles = rows
 
-    # 3) mirror first article -> single field + refresh the display label
+    # 3) refresh the per-row "Tax Articles" display label
     by_row = {}
     for r in rows:
         by_row.setdefault(r.parent_row, []).append(r.tax_article)

jey_erp/custom_fields.py

@@ -731,7 +731,9 @@ def create_custom_fields():
                 insert_after='act_type',
                 depends_on='eval:doc.purchase_type && doc.act_type == "Import"'
             ),
-            # --- TEST: backing store for per-item multi tax-article ---
+            # Per-item multiple tax articles: parent-level backing table,
+            # linked to each item row by custom_si_row_key (Frappe has no
+            # nested child tables, so this lives on the parent, not the row).
             dict(
                 fieldname='custom_item_tax_articles_section',
                 label='Item Tax Articles',