Registering multiple agents in program initialization creates a 'last man wins' situation'

[MattB-msft]

Describe the bug
If I have a program file that includes the following code:

// Add AgentApplicationOptions from appsettings config.
builder.AddAgentApplicationOptions();

// Add the Agent
builder.AddAgent<AuthAgent>();
builder.AddAgent<AuthAgent2>();

Where AuthAgent and AuthAgent2 are both AgentApplications,

The SDK Accepts this however only ever calls the 'last' agent registered.
There does not seem to be a way to attach a route or port to ither agent independently, or call for a named agent in the code:

app.MapPost("/api/messages", async (HttpRequest request, HttpResponse response, IAgentHttpAdapter adapter, IAgent agent, CancellationToken cancellationToken) =>
    {
        await adapter.ProcessAsync(request, response, agent, cancellationToken);
    })
    .AllowAnonymous();

We should either disallow multiple agents to be registered or provide a means to map a route by type or name.