feat(samples): add basic clustering sample

[ReubenBond]

Problem

The repository did not have a focused sample showing newcomers how more than one Orleans silo forms a cluster. The original MembershipTableGrain approach requested by #4547 is obsolete, while existing multi-silo samples also demonstrate unrelated application features.

Solution

Add a self-contained Basic Clustering sample which uses Aspire to start two silo replicas and Redis for membership and gateway discovery. The sample reports membership changes, makes the same grain call from both silos, includes safe local-versus-production guidance, and is registered in the sample gallery.

Rationale

This keeps the learning path small while demonstrating the current external membership-provider model and automatic per-replica endpoint configuration. The README also identifies UseLocalhostClustering and UseDevelopmentClustering as development-only in-memory alternatives instead of presenting them as production configuration.

Fixes #4547

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Adds a new Basic Clustering sample under samples/ to demonstrate how multiple Orleans silo processes form a cluster, using Aspire for orchestration and Redis for membership/gateway discovery. This fits the repository’s samples gallery as a focused, minimal multi-silo onboarding step.

Changes:

• Added a new samples/BasicClustering sample (AppHost + Silo) showing a 2-replica Orleans cluster using Redis membership via Aspire.
• Registered the sample in the gallery manifest and regenerated the samples index README entry.
• Included the new sample projects in samples/Samples.slnx for validation/build.

Show a summary per file

File	Description
samples/Samples.slnx	Adds the BasicClustering projects to the samples solution.
samples/README.md	Updates the generated sample index to include Basic Clustering.
samples/gallery.json	Registers the Basic Clustering sample in the gallery manifest.
samples/BasicClustering/README.md	Documents what the sample demonstrates and how to run it via Aspire.
samples/BasicClustering/Directory.Packages.props	Declares centrally-managed package versions for the sample.
samples/BasicClustering/BasicClustering.slnx	Adds a sample-local solution including AppHost and Silo projects.
samples/BasicClustering/BasicClustering.Silo/Program.cs	Configures the silo host to use Aspire-provided Redis and Orleans hosting.
samples/BasicClustering/BasicClustering.Silo/IHelloGrain.cs	Introduces a minimal grain contract used by the sample.
samples/BasicClustering/BasicClustering.Silo/HelloGrain.cs	Implements the hello grain returning runtime identity info.
samples/BasicClustering/BasicClustering.Silo/ClusterMonitor.cs	Adds a background service which logs membership and performs a cross-silo grain call.
samples/BasicClustering/BasicClustering.Silo/BasicClustering.Silo.csproj	Defines the silo project and required package references.
samples/BasicClustering/BasicClustering.AppHost/Properties/launchSettings.json	Sets local Aspire dashboard/host launch configuration.
samples/BasicClustering/BasicClustering.AppHost/Program.cs	Defines the Aspire app host, Redis resource, and 2-replica silo project.
samples/BasicClustering/BasicClustering.AppHost/BasicClustering.AppHost.csproj	Defines the AppHost project using Aspire.AppHost.Sdk and references the silo project.

Review details

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• Files reviewed: 14/14 changed files
• Comments generated: 1
• Review effort level: Lite

[Copilot]

Review details

• Files reviewed: 14/14 changed files
• Comments generated: 0 new
• Review effort level: Lite