refactor: update model input and output types to use ContextInput and Result

[Ki-Seki]

No description provided.

[Copilot]

Pull Request Overview

This PR refactors the model input and output types to improve type safety and consistency across the codebase. The changes standardize the handling of context inputs and model outputs by introducing clearer type definitions and a unified approach to result generation.

Key changes:

• Replace Response type with Result type for model outputs
• Standardize model input types to use ContextInput type alias
• Update result creation to use infill() function instead of direct Response() construction

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/models/test_openai.py	Updates test assertions to use Result instead of Response type
src/gimkit/models/utils.py	Refactors input/output types and changes result creation to use infill()
src/gimkit/models/openai.py	Updates type annotations to use new ContextInput and Result types
examples/gimkit_quickstart.py	Modernizes example to use model integration instead of manual LLM requests
examples/cases.ipynb	Updates notebook examples to use new model interface

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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