fix: correct v2.0.0 changelog date to 2026-02-18

Author: zebbern

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/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [2.0.0] - 2025-06-19
+## [2.0.0] - 2026-02-18
 
 ### Breaking Changes
 - Migrated from deprecated `@anthropic-ai/claude-code` to `@anthropic-ai/claude-agent-sdk` v0.2.45