fix: Make sure Tool information attached to ContentToolRequest is serializable

[cpsievert]

Follow up to #156, which broke .model_dump_json() of ContentToolRequest, which in turn breaks bookmarking of tool calls.

While here, I decided that it's not worth supporting from mcp.type import ToolAnnotations to support annotations, and instead maintain our own TypedDict.

[Copilot]

Pull Request Overview

This PR fixes a serialization issue with ContentToolRequest objects by replacing direct Tool instances with serializable ToolInfo objects, while also moving away from MCP's ToolAnnotations to maintain a custom TypedDict implementation.

• Creates a new ToolInfo class containing only serializable tool metadata
• Replaces MCP's ToolAnnotations with a custom TypedDict implementation
• Updates all test code to use ToolInfo.from_tool() when creating ContentToolRequest objects

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
chatlas/_content.py	Adds ToolInfo class and ToolAnnotations TypedDict for serializable tool metadata
chatlas/_tools.py	Updates to use custom ToolAnnotations and convert MCP annotations to dict format
chatlas/_chat.py	Modifies tool request handling to use ToolInfo instead of direct Tool references
chatlas/_typing_extensions.py	Changes Python version requirement for TypedDict imports
tests/test_content_tools.py	Adds serialization test and updates existing tests to use ToolInfo
tests/test_tools_enhanced.py	Updates all test cases to use ToolInfo.from_tool() pattern
tests/test_tool_from_mcp.py	Updates MCP tool annotation tests to use dict access
tests/conftest.py	Updates to use custom ToolAnnotations instead of MCP version
chatlas/init.py	Exports new ToolInfo and ToolAnnotations types
CHANGELOG.md	Documents breaking change and bug fix

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}