9a1fee379c
Address PR review feedback: Instead of using **capability_extensions to spread arbitrary keys into ClientCapabilities, explicitly use the 'extensions' field. This prevents potential conflicts if new fields are added to ClientCapabilities in the future. Changes: - Add 'extensions' field to ClientCapabilities type definition - Update ClientSession to pass capability_extensions as 'extensions' kwarg - Update test to pass extensions dict directly (without 'extensions' key wrapper)