Ensure GPT-5.2-codex has variants

Improvements

• CoreAdjust Codex styling and fix hint display
• CoreUpdate docs and authentication methods for OpenAI
• CoreImprove Codex instructions prompt for better task planning
• CoreAdd Codex authentication support
• TerminalFix instance disposal to prevent memory leaks and dangling references
• CoreAdd ChatGPT-Account-Id header for organization subscriptions@fdematos