Improve client registration guidance

[alexwolfmsft]

Summary

Describe your changes here.

Fixes #Issue_Number (if available)

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Internal previews

📄 File	🔗 Preview link
docs/azure/sdk/aspnetcore-guidance.md	Use the Azure SDK for .NET in ASP.NET Core apps
docs/azure/sdk/authentication/best-practices.md	[ASP.NET Core](https://review.learn.microsoft.com/en-us/dotnet/azure/sdk/authentication/best-practices?branch=pr-en-us-49938)
docs/azure/sdk/dependency-injection.md	Dependency injection with the Azure SDK for .NET
docs/azure/sdk/logging.md	Logging with the Azure SDK for .NET

[Copilot]

Pull request overview

This PR improves client registration guidance by clarifying that DefaultAzureCredential is automatically applied when using AddAzureClients, reducing unnecessary boilerplate code and preventing confusion about credential setup.

Key changes:

• Removed redundant explicit UseCredential(new DefaultAzureCredential()) calls from code samples where credentials weren't being reused
• Added explanatory comments in samples that retain explicit credential creation to clarify when and why manual credential creation is needed
• Updated documentation to explain the implicit DefaultAzureCredential behavior
• Improved error handling in subclient registration with explicit null checking via pattern matching
• Updated code highlight ranges to reflect the modified code structure

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/azure/sdk/snippets/pagination/Program.cs	Removed redundant UseCredential call since credential isn't reused elsewhere
docs/azure/sdk/snippets/dependency-injection/WebApplicationBuilder/Program.cs	Added clarifying comments about implicit credential creation, improved subclient registration with pattern matching for null handling, updated variable naming from queue to queueName
docs/azure/sdk/snippets/dependency-injection/HostBuilder/Program.cs	Added clarifying comments about implicit credential creation, improved subclient registration with pattern matching for null handling, updated variable naming from queue to queueName
docs/azure/sdk/snippets/dependency-injection/HostApplicationBuilder/Program.cs	Added clarifying comments about implicit credential creation, improved subclient registration with pattern matching for null handling, standardized comment text with other samples
docs/azure/sdk/snippets/authentication/local-dev-account/Program.cs	Removed redundant UseCredential call from the simple registration example
docs/azure/sdk/snippets/authentication/credential-chains/Program.cs	Removed redundant explicit credential creation and UseCredential call from basic example
docs/azure/sdk/snippets/aspnetcore-guidance/MinApiSample/Program.cs	Removed redundant UseCredential call since credentials aren't reused
docs/azure/sdk/snippets/aspnetcore-guidance/BlazorSample/Program.cs	Removed redundant UseCredential call and associated comment
docs/azure/sdk/logging.md	Updated description to clarify that DefaultAzureCredential is applied automatically
docs/azure/sdk/dependency-injection.md	Updated explanatory text to clarify implicit credential behavior, removed redundant UseCredential calls from configuration examples, updated code highlight ranges
docs/azure/sdk/authentication/best-practices.md	Updated example description to clarify the implicit credential usage, removed code highlighting from the simplified example
docs/azure/sdk/aspnetcore-guidance.md	Updated code range references to reflect modified snippets, revised explanation to clarify implicit credential behavior