docs(changelog): cut the 2.4.0 release

Author: obeone

CHANGELOG.md

@@ -10,6 +10,8 @@ and rename that heading to the version when you cut the release.
 
 ## [Unreleased]
 
+## [2.4.0](https://github.com/obeone/caucus-mcp/compare/v2.3.1...v2.4.0) (2026-08-20)
+
 ### Fixed
 
 - **A reviving peer no longer wakes the whole room.** When an idle-dropped peer
@@ -628,7 +630,7 @@ history for per-commit detail):
   dashboard WebSocket protocol with auth/RBAC and static asset serving, richer
   peer/health state with per-peer pause, and an opt-in JSONL event log.
 
-[Unreleased]: https://github.com/obeone/caucus-mcp/compare/v2.3.1...HEAD
+[Unreleased]: https://github.com/obeone/caucus-mcp/compare/v2.4.0...HEAD
 [1.2.1]: https://github.com/obeone/caucus-mcp/compare/v1.2.0...v1.2.1
 [1.2.0]: https://github.com/obeone/caucus-mcp/compare/v1.1.0...v1.2.0
 [1.1.0]: https://github.com/obeone/caucus-mcp/compare/v1.0.0...v1.1.0