chore(changelog): add compiler change entry

Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Author: Copilot

.chronus/changes/copilot-fix-html-program-viewer-crash-2026-5-26-18-32-40.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+Fix diagnostic target node mapping for value entities.