V3 FluentBuilder validation failed when an operation references a component message

### I tried this:

I tried to build an AsyncAPI v3 document using the FluentBuilder API where an operation references a message.

Minimal reproducible example (reduced from the README):

```csharp
[Fact]
public void Validate_FluentBuilder_Should_Valid()
{
var channelParameterSchema = new JsonSchemaBuilder().FromType();
var builder = ServiceProvider.GetRequiredService();
var doc = builder
.WithTitle("Cloud Event API")
.WithVersion("1.0.0")
.WithServer("StreetLightsApi", server => server
.WithHost("https://streetlights.fake.com")
.WithProtocol(AsyncApiProtocol.Http, "2.0")
.WithBinding(new HttpServerBindingDefinition()))
.WithChannel("events", channel => channel
.WithServer("#/servers/StreetLightsApi")
.WithDescription("The endpoint used to publish and subscribe to cloud events")
.WithBinding(new HttpChannelBindingDefinition())
.WithMessage("lightMeasuredEvent", definitionBuilder => { }))
.WithOperation("observeCloudEvents", operation => operation
.WithAction(V3OperationAction.Send)
.WithChannel("#/channels/events")
.WithTitle("ObserveCloudEvents")
.WithDescription("Observes cloud events published by the StreetLightsApi")
.WithBinding(new HttpOperationBindingDefinition
{
Method = HttpMethod.POST,
Type = HttpBindingOperationType.Response
})
.WithMessage("#/components/messages/lightMeasuredEvent"))
.WithMessageComponent("lightMeasuredEvent", message => message
.WithName("LightMeasuredEvent")
.WithDescription("The event fired whenever the luminosity of a light has been measured")
.WithContentType("application/json"))
.Build();
}
```

### This happened:

`Build()` throws a `FluentValidation.ValidationException`:

```
Validation failed:
-- Operations.Values[0].Messages[0]:
The operation must reference a message defined by the channel it belongs to
```

### I expected this:

_No response_

### Is there a workaround?

_No response_

### Anything else?

Root cause analysis:
- `V3OperationMessageValidator ` enforces that operation messages must reference channel messages only
- During validation, `DereferenceChannelMessage(...)` is called with a reference like
`#/components/messages/lightMeasuredEvent`
- This method explicitly rejects non-channel references and throws an `InvalidDataException`, which causes the validator to fail

### Platform(s)

Windows

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