docs: add agents.md

[JP-Ellis]

📝 Summary

Add generic AGENTS.md file as the open standard for AI-focused instructions.

🚨 Breaking Changes

🔥 Motivation

To make this repository more accessible.

🔨 Test Plan

🔗 Related issues/PRs

[Copilot]

Pull Request Overview

This PR adds a new AGENTS.md file containing AI-focused documentation that provides a quick reference guide for AI agents working with the Pact Python project. The file serves as a comprehensive guide covering development commands, code style guidelines, testing practices, and project structure.

• Adds structured documentation specifically designed for AI agents
• Provides quick reference for common development tasks and project standards
• Documents the project structure and component organization

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52%. Comparing base (d474a6e) to head (7540187).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

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  Coverage    52%     52%           
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  Files        32      32           
  Lines      3739    3739           
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  Hits       1966    1966           
  Misses     1773    1773           

Flag	Coverage Δ
tests	52% <ø> (ø)

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