DI Refactor: Azure.Mcp.Tools.Policy

[Copilot]

Part of the broader DI refactor (#158) — removes context.GetService<IPolicyService>() from ExecuteAsync in favor of constructor injection.

Changes

• PolicyAssignmentListCommand: Added IPolicyService as a constructor parameter; replaced runtime service resolution with the injected field.
• PolicyAssignmentListCommandTests: Pass mock service directly to constructor; removed ServiceCollection registration of the mock.

Before:

public sealed class PolicyAssignmentListCommand(ILogger<PolicyAssignmentListCommand> logger)
    : SubscriptionCommand<PolicyAssignmentListOptions>
{
    public override async Task<CommandResponse> ExecuteAsync(...)
    {
        var policyService = context.GetService<IPolicyService>();
        var assignments = await policyService.ListPolicyAssignmentsAsync(...);
    }
}

After:

public sealed class PolicyAssignmentListCommand(ILogger<PolicyAssignmentListCommand> logger, IPolicyService policyService)
    : SubscriptionCommand<PolicyAssignmentListOptions>
{
    private readonly IPolicyService _policyService = policyService;

    public override async Task<CommandResponse> ExecuteAsync(...)
    {
        var assignments = await _policyService.ListPolicyAssignmentsAsync(...);
    }
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>DI Refactor: Azure.Mcp.Tools.Policy</issue_title>
<issue_description>## Summary

Refactor Azure.Mcp.Tools.Policy to use constructor dependency injection instead of resolving services via context.GetService<T>() in ExecuteAsync.

This is a sub-issue of #158.

Instructions

Follow the algorithm described in tools/di-refactor-plan.md with {ToolArea} = Policy.

An example PR is: #1815
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes DI Refactor: Azure.Mcp.Tools.Policy #1864

---

📱 Kick off Copilot coding agent tasks wherever you are with GitHub Mobile, available on iOS and Android.