[breaking] OpenAI deprecates original GPT-5 and o3 snapshots, shutdown December 2026

The original GPT-5 snapshots (gpt-5, mini, nano, pro) and the o3/o3-pro snapshots were deprecated June 11, 2026 and shut down December 11, 2026. Replacements per model: gpt-5.5, gpt-5.4-mini, gpt-5.4-nano, and gpt-5.5-pro. Effective: 2026-12-11. Affected: openai/gpt-5-2025-08-07, openai/gpt-5-mini-2025-08-07, openai/gpt-5-nano-2025-08-07, openai/gpt-5-pro-2025-10-06, openai/o3-2025-04-16, openai/o3-pro-2025-06-10. Severity: breaking. Verification: verified.