docs add vulnerability triage changelog

Author: msukkari

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 - Vulnerability triage now keeps Linear issues synchronized with current security findings.
+- Fixed vulnerability triage for reusable-workflow callers and repositories without CodeQL. [#1515](https://github.com/sourcebot-dev/sourcebot/pull/1515)
 
 ## [5.1.4] - 2026-07-24