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This pull request is related to:

• A bug
• A new feature
• Documentation
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I have checked the following:

• I have read and understood the contribution guidelines and the code of conduct;
• I have added new tests (for bug fixes/features);
• I have added/updated the documentation (for bug fixes / features).

Description:
Add support for Claude 4.5 Opus model (claude-opus-4-5-20251101) to the anthropic plugin.

Changes:

• Added claude45Opus model reference in claude.ts
• Added model to SUPPORTED_CLAUDE_MODELS mapping
• Exported model from index.ts
• Updated README to list all supported Claude models including Claude 4.x series

Related issues:
None