feat: add GPT-5.6 variants to Bedrock catalog

[celia-oai]

Summary

• add Sol (openai.gpt-5.6-sol), Terra (openai.gpt-5.6-terra), and Luna (openai.gpt-5.6-luna) to the Amazon Bedrock static model catalog
• derive all three entries from the bundled GPT-5.5 metadata and add the Bedrock-only max reasoning effort
• keep the new entries below the current GPT-5.5 and GPT-5.4 models at priorities 2, 3, and 4, preserving GPT-5.5 as the default
• add deep-equality coverage for inherited model configuration, catalog ordering, context windows, and service-tier behavior

[chatgpt-codex-connector]

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