Simplify readme generator test services and remove noisy test logging

[benbp]

This updates the readme generator tests to not use the service provider for setup, which was causing a lot of logs to get printed out when tests are passing. Instead we now inject TestLogger manually.

FYI @richardpark-msft

[Copilot]

Pull Request Overview

This PR simplifies the README generator test services by removing complex mocking infrastructure and reduces noise from test logging. The changes focus on making tests more maintainable and eliminating verbose output during test execution.

• Replaced complex TestClients record and service provider setup with direct mock injection
• Changed logging level from LogInformation to LogDebug to reduce noise during agent cleanup operations
• Renamed MockOutputHelper to TestOutputHelper for better clarity

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
AzureAgentService.cs	Changed logging level from Information to Debug for agent cleanup operations
ReadMeGeneratorToolTests.cs	Simplified test setup by removing complex service provider configuration and using direct mock injection
MockOutputHelper.cs	Renamed class to TestOutputHelper and updated documentation

Comments suppressed due to low confidence (1)

tools/azsdk-cli/Azure.Sdk.Tools.Cli/Services/Azure/Agent/AzureAgentService.cs:1

• The model version 'gpt-4.1-mini' does not exist. Valid GPT-4 model names include 'gpt-4', 'gpt-4-turbo', 'gpt-4o', and 'gpt-4o-mini'. Consider using 'gpt-4o-mini' instead.

using Azure.AI.Agents.Persistent;