use new function call interface

[bddap]

https://openai.com/blog/function-calling-and-other-api-updates

[Copilot]

PR Overview

This PR updates the function call interface as described in the linked blog post by introducing a new module to define capabilities and updating message serialization to support function calls. Key changes include adding the new "powers" module with various capabilities, refactoring the Message data type to support function call information, and updating dependencies and documentation accordingly.

Reviewed Changes

File	Description
src/powers.rs	New module defining capabilities with a function spec interface.
src/api.rs	Refactored Message enum to include function call fields and helpers.
README.md	Updated examples and documentation for refac commands.
src/main.rs	Integrated the new function spec interface into the refactor flow.
Cargo.toml	Added dependencies needed for the new features.
src/common.rs	Removed an ignored test related to diff processing.

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.