docs: update v0.5.3 changelog with additional bug fixes

Add checkpoint linkage preservation after history rewrites (#840) and
fail-closed content detection in prepare-commit-msg (#826). Update
release date to 2026-04-03.

Signed-off-by: Paulo Gomes <paulo@entire.io>
Assisted-by: Claude Opus 4.6 <noreply@anthropic.com>
Entire-Checkpoint: 0154164ac0f9

Author: pjbgf

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/),
 and this project adheres to [Semantic Versioning](https://semver.org/).
 
-## [0.5.3] - 2026-04-02
+## [0.5.3] - 2026-04-03
 
 ### Added
 
@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 - Resume failing when checkpoints aren't fetched locally yet ([#796](https://github.com/entireio/cli/pull/796))
 - OpenCode transcript export resilient to stdout truncation ([#832](https://github.com/entireio/cli/pull/832))
+- Fail-closed content detection in `prepare-commit-msg` to prevent dangling checkpoint trailers from stale sessions ([#826](https://github.com/entireio/cli/pull/826))
 
 ### Housekeeping