feat(models): support GPT-6 and Claude 5 families

[roackb2]

Summary

• Add opt-in GPT-6 Astra, Sol, and Luna plus Claude Fable 5.1, Opus 5.5, and Sonnet 5.5 to the curated model catalog.
• Align context and reasoning-effort policy, and update the Anthropic SDK and Messages request path.
• Preserve private signed Claude thinking blocks across tool turns and persisted sessions; keep existing default models unchanged.

Verification

• yarn build
• yarn typecheck
• yarn lint
• yarn test: 985 unit and 475 integration tests passed
• Live Heddle CLI: each GPT-6 model completed a one-step OK prompt. GPT-6 Luna also completed a saved two-turn conversation with list_files, read_file, and search_files calls.

Review limit

• Anthropic rejected the bounded live Sonnet 5.5 smoke because the API account lacked credit. Fable, Opus, and live Claude tool turns remain unverified; mocked adapter and persistence tests pass.
• No Claude subscription sign-in, package release, or deployment is included.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-29T09:38:21.853963Z	9b44d01	Draft marked ready

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