chore: bump version to 2.4.3

- Fix critical Node.js DEP0190 security vulnerability in Windows npm package
- Add proper argument escaping to prevent command injection attacks
- Update all spawn() calls with platform-specific handling
- Add comprehensive changelog entry for security fix
- Maintain full cross-platform compatibility

Security fix resolves deprecation warning and secures Windows installations.

lib/ccs

@@ -2,7 +2,7 @@
 set -euo pipefail
 
 # Version (updated by scripts/bump-version.sh)
-CCS_VERSION="2.4.1"
+CCS_VERSION="2.4.3"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
 # --- Color/Format Functions ---

lib/ccs.ps1

@@ -72,7 +72,7 @@ Restart your terminal after installation.
 }
 
 # Version (updated by scripts/bump-version.sh)
-$CcsVersion = "2.4.1"
+$CcsVersion = "2.4.3"
 $ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
 
 # Installation function for commands and skills