Follow-up on test platforms docs refactoring

[Evangelink]

Summary

Follow-up from #51854

---

Internal previews

📄 File	🔗 Preview link
docs/core/testing/microsoft-testing-platform-architecture-extensions.md	Build extensions for Microsoft.Testing.Platform
docs/core/testing/microsoft-testing-platform-architecture-test-framework.md	Build a test framework
docs/core/testing/microsoft-testing-platform-extensions-vstest-bridge.md	Microsoft.Testing.Platform VSTest bridge extension
docs/core/testing/microsoft-testing-platform-fakes.md	Microsoft Fakes
docs/core/testing/microsoft-testing-platform-features.md	docs/core/testing/microsoft-testing-platform-features
docs/core/testing/microsoft-testing-platform-retry.md	Retry
docs/core/testing/microsoft-testing-platform-test-reports.md	Test reports
docs/core/testing/microsoft-testing-platform-troubleshooting.md	Microsoft.Testing.Platform troubleshooting
docs/core/testing/test-platforms-overview.md	Test platforms overview for .NET

[Copilot]

Pull request overview

Follow-up documentation refinements to the .NET testing platform content, focusing on clarifying platform selection guidance and updating Microsoft.Testing.Platform (MTP) reference pages after the earlier refactor in #51854.

Changes:

• Update platform selection guidance (including new scenarios and updated dotnet test notes).
• Refresh MTP docs (retry API call shape, TRX report details, exit code list, and various wording/title improvements).
• Adjust MTP architecture docs to reflect updated guidance and API surface descriptions.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
docs/core/testing/test-platforms-overview.md	Updates guidance on choosing VSTest vs MTP, including new scenarios and revised mixing/dotnet-test messaging.
docs/core/testing/microsoft-testing-platform-troubleshooting.md	Updates the documented exit code list (marks exit code 5 as no longer produced).
docs/core/testing/microsoft-testing-platform-test-reports.md	Adds guidance about manual TRX provider registration order and updates the default TRX filename format description.
docs/core/testing/microsoft-testing-platform-retry.md	Updates manual registration example to use builder.AddRetryProvider().
docs/core/testing/microsoft-testing-platform-features.md	Refines scenario navigation text (telemetry phrasing).
docs/core/testing/microsoft-testing-platform-fakes.md	Updates article title metadata for clarity.
docs/core/testing/microsoft-testing-platform-extensions-vstest-bridge.md	Rewords the intro to better position the bridge extension’s purpose.
docs/core/testing/microsoft-testing-platform-architecture-test-framework.md	Updates architecture guidance and type descriptions for ITestFramework and related APIs.
docs/core/testing/microsoft-testing-platform-architecture-extensions.md	Clarifies the page title and section naming for extension points.

Comments suppressed due to low confidence (1)

docs/core/testing/test-platforms-overview.md:50

• The dotnet test row for MTP omits the key pre-.NET 10 behavior (VSTest mode via TestingPlatformDotnetTestSupport plus the extra -- separator), which is still documented elsewhere (for example, migrating-vstest-microsoft-testing-platform.md and unit-testing-with-dotnet-test.md). Consider adding a brief “In .NET 9 SDK and earlier…” note here (or explicitly defer to the linked unit-testing-with-dotnet-test.md) to avoid misleading readers on older SDKs.

| `dotnet test` behavior | Default VSTest mode. VSTest arguments and behavior apply. | Native MTP mode is available in .NET 10 SDK and later. |