chore: add changelog entry for zoekt upstream sync

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: msukkari

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- Synced `vendor/zoekt` with upstream `sourcegraph/zoekt`. [#1140](https://github.com/sourcebot-dev/sourcebot/pull/1140)
+
 ## [4.16.12] - 2026-04-20
 
 ### Fixed