docs: add comprehensive AI SDK 6 tool execution documentation
- Document override patterns (complete, conditional, schema-only)
- Document extension patterns (pre/post processing, retry, caching, validation)
- Add custom middleware implementation guide
- Add factory pattern for maximum flexibility
- Include complete examples combining TPMJS tools with custom tools
- Cover best practices for error handling, timeouts, rate limiting, security
- Add API reference for registrySearchTool and registryExecuteTool
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Co-Authored-By: Claude <noreply@anthropic.com>
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