Add XML documentation and update diagnostic ID to ASPIREPIPELINES004

- Update Experimental attribute from ASPIREPIPELINES001 to ASPIREPIPELINES004
- Add XML documentation for GetOutputDirectory() default behavior
- Add XML documentation for private fields in PipelineOutputService
- Document purpose of AppHost:PathSha256 usage in CreateTempDirectory
- Suppress ASPIREPIPELINES004 diagnostic in all consuming files

Co-authored-by: captainsafia <1857993+captainsafia@users.noreply.github.com>

Author: Copilot

src/Aspire.Hosting.Azure/AzureEnvironmentResource.cs

@@ -4,6 +4,7 @@
 #pragma warning disable ASPIREAZURE001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
 #pragma warning disable ASPIREPIPELINES003 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
 #pragma warning disable ASPIREINTERACTION001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
+#pragma warning disable ASPIREPIPELINES004 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
 
 using System.Diagnostics.CodeAnalysis;
 using Aspire.Hosting.ApplicationModel;

src/Aspire.Hosting/DistributedApplicationBuilder.cs

@@ -4,6 +4,7 @@
 #pragma warning disable ASPIREPIPELINES003
 #pragma warning disable ASPIREPIPELINES001
 #pragma warning disable ASPIREPIPELINES002
+#pragma warning disable ASPIREPIPELINES004
 
 using System.Diagnostics;
 using System.Reflection;

src/Aspire.Hosting/Pipelines/IPipelineOutputService.cs

@@ -9,11 +9,12 @@ namespace Aspire.Hosting.Pipelines;
 /// <summary>
 /// Service for managing pipeline output directories.
 /// </summary>
-[Experimental("ASPIREPIPELINES001", UrlFormat = "https://aka.ms/aspire/diagnostics/{0}")]
+[Experimental("ASPIREPIPELINES004", UrlFormat = "https://aka.ms/aspire/diagnostics/{0}")]
 public interface IPipelineOutputService
 {
     /// <summary>
     /// Gets the output directory for deployment artifacts.
+    /// If no output path is configured, defaults to <c>{CurrentDirectory}/aspire-output</c>.
     /// </summary>
     /// <returns>The path to the output directory for deployment artifacts.</returns>
     string GetOutputDirectory();

src/Aspire.Hosting/Pipelines/PipelineOutputService.cs

@@ -11,10 +11,17 @@ namespace Aspire.Hosting.Pipelines;
 /// <summary>
 /// Default implementation of <see cref="IPipelineOutputService"/>.
 /// </summary>
-[Experimental("ASPIREPIPELINES001", UrlFormat = "https://aka.ms/aspire/diagnostics/{0}")]
+[Experimental("ASPIREPIPELINES004", UrlFormat = "https://aka.ms/aspire/diagnostics/{0}")]
 internal sealed class PipelineOutputService : IPipelineOutputService
 {
+    /// <summary>
+    /// Stores the resolved output directory path, or <c>null</c> if not specified.
+    /// </summary>
     private readonly string? _outputPath;
+    
+    /// <summary>
+    /// Lazily creates and stores the path to the temporary directory for pipeline output.
+    /// </summary>
     private readonly Lazy<string> _tempDirectory;
 
     public PipelineOutputService(IOptions<PipelineOptions> options, IConfiguration configuration)
@@ -53,6 +60,12 @@ public string GetTempDirectory(IResource resource)
         return Path.Combine(baseTempDir, resource.Name);
     }
 
+    /// <summary>
+    /// Creates a temporary directory for pipeline build artifacts.
+    /// Uses AppHost:PathSha256 from configuration to create an isolated temp directory per app host,
+    /// enabling multiple app hosts to run concurrently without conflicts.
+    /// If AppHost:PathSha256 is not available, falls back to a generic "aspire" temp directory.
+    /// </summary>
     private static string CreateTempDirectory(IConfiguration configuration)
     {
         var appHostSha = configuration["AppHost:PathSha256"];

src/Shared/PublishingContextUtils.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 #pragma warning disable ASPIREPIPELINES001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
+#pragma warning disable ASPIREPIPELINES004 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
 
 using Aspire.Hosting.ApplicationModel;
 using Aspire.Hosting.Pipelines;

tests/Aspire.Hosting.Tests/Helpers/JsonDocumentManifestPublisher.cs

@@ -3,6 +3,7 @@
 
 #pragma warning disable CS0618 // Type or member is obsolete
 #pragma warning disable ASPIREPIPELINES001
+#pragma warning disable ASPIREPIPELINES004
 
 using System.Text.Json;
 using Aspire.Hosting.Publishing;