Add C# examples to circuit breaker documentation page

[currantw]

Description

The circuit breaker documentation page at https://glide.valkey.io/how-to/connections/circuit-breaker/ currently shows "The circuit breaker is not yet available in the C# client" under the C# tab for both the Configuration and Handling Rejections sections.

Circuit breaker support is being added to the C# client in valkey-io/valkey-glide-csharp#474. Once that PR is merged, the C# tab should be updated with:

• Configuration example using CircuitBreakerConfig with fluent WithXxx() methods
• Exception handling example catching CircuitBreakerException

C# API (for docs authors)

// Configuration
var cb = new CircuitBreakerConfig()
    .WithWindowSize(TimeSpan.FromSeconds(15))
    .WithFailureRateThreshold(0.6)
    .WithCountTimeouts(true);

var config = new ConnectionConfiguration.StandaloneClientConfigurationBuilder()
    .WithAddress("localhost", 6379)
    .WithCircuitBreaker(cb)
    .Build();

var client = await GlideClient.CreateClient(config);

// Handling rejections
try
{
    await client.SetAsync("key", "value");
}
catch (Errors.CircuitBreakerException)
{
    // Circuit breaker is open — requests are being rejected
}

Context

• C# implementation PR: task(config): Add circuit breaker configuration support valkey-glide-csharp#474
• Class: Valkey.Glide.CircuitBreakerConfig
• Exception: Valkey.Glide.Errors.CircuitBreakerException