Harden GXByteArray capacity management

[gvtret]

Summary

• add a private capacity helper and grow-on-demand logic that keeps CGXByteArray state consistent on allocation failure paths
• harden indexed writes, zero-fill, and append helpers to guard against overflow, update size correctly, and respect requested string lengths
• improve ToArray and buffer copy helpers to handle allocation failure and propagate errors from buffer sources

[sonarqubecloud]

Quality Gate passed

Issues
17 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud