Fix validation error in copilot agent

[ar90n]

This PR is motivated to fix #25 by adding workaround codes for Copilot Agent.
This PR contains following modifications.

• Add a custom Json Schema generator whose name is CopilotAgentCompatibleSchema. This generator handles tuple type to add items field.
• Override model_json_schema to use CopilotAgentCompatibleSchema as default.

Folowing result is the differences between original JsonSchema and modified JsonSchema. In this result, org.json means original JsonSchema and mod.json means modified JsonSchema.

diff org.json mod.json
157a158
>                         "items": {},
345a347
>                         "items": {},
532a535
>                         "items": {},

We can see that there are only adding "items": {} .
And after this PR applied, we get following. It seems that mcp-server-docker works expectedly.

[ckreiling]

Hey thank you for your contribution! My plan is to pull this branch down locally and test with Claude Desktop to make sure it doesn't introduce any regressions. I will review this PR in the coming days - thanks for your patience