Fix SQL MERGE column references

changelog.d/unreleased/2100.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 2100
+affected:
+  - src/CodeIndex/Indexer/References/Languages/SqlReferenceExtractor.cs
+  - tests/CodeIndex.Tests/ReferenceExtractorTests.cs
+---
+
+## English
+
+- **SQL MERGE actions now emit column-level reference edges (#2100)** — `MERGE` extraction now records `column_reference` edges from `UPDATE SET`, `INSERT (...)`, and `VALUES (...)` action bodies, plus `join_condition_reference` edges from the `ON` predicate, so lineage and impact queries can follow MERGE-driven transformations more completely.
+
+## 日本語
+
+- **SQL MERGE action が列レベルの reference edge を出すようになりました (#2100)** — `MERGE` 抽出は `UPDATE SET`、`INSERT (...)`、`VALUES (...)` の action body から `column_reference` edge を、`ON` 条件から `join_condition_reference` edge を記録するようになり、MERGE による変換の lineage / impact query がより完全に追跡できます。