chore(mcp): add changelog entry for @modelcontextprotocol/sdk bump to 1.26.0

Co-authored-by: Brendan Kellam <brendan-kellam@users.noreply.github.com>

Author: github-actions[bot]

packages/mcp/CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- Bumped `@modelcontextprotocol/sdk` from 1.10.2 to 1.26.0. [#958](https://github.com/sourcebot-dev/sourcebot/pull/958)
+
 ## [1.0.17] - 2026-02-19
 
 ### Added