Update development tools and dependencies

[djthorpe]

This pull request improves the handling of tools with a nil input schema in the server code, ensuring they are accepted and default to an empty object schema. It also adds a test to verify this behavior.

Input schema handling improvements:

• Updated sdkToolFromTool in mcp/server/tool.go to default any nil input schema to an empty object schema using jsonschema.MustFor[struct{}](), ensuring all tools have a valid input schema.
• Added the jsonschema import to support the new defaulting behavior.

Testing enhancements:

• Added a new test tool, nilInputSchemaTool, and a corresponding test case, TestAddToolsNilInputSchemaDefaultsToEmptyObject, in mcp/server/tool_test.go to verify that tools with a nil input schema are accepted without error.
• Added the missing llm import in the test file to support the new test tool implementation.

[Copilot]

Pull request overview

This PR updates the MCP server’s tool conversion to handle nil tool input schemas by defaulting them to an empty-object JSON schema, and adds a regression test around that behavior.

Changes:

• Default llm.Tool.InputSchema() from nil to jsonschema.MustFor[struct{}]() during SDK tool conversion.
• Add a new test tool and test case intended to verify nil input schema handling.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
mcp/server/tool.go	Defaults nil tool input schemas to an empty-object JSON schema before marshalling into the SDK Tool.
mcp/server/tool_test.go	Adds a test tool with nil InputSchema and a test case for server tool registration behavior.