.NET Multi-Agent Orchestration Timeout and Cancellation Handling

@alliscode is already working on this.

Since Dec 9, 2025.

Current Behavior: When orchestrating multiple agents sequentially or in parallel, there's no built-in timeout handling. Long-running agent calls (20-40s each) can cascade into multiple-minute delays without proper circuit breakers.

Problem: Production systems need timeout protection:

Individual agent calls may hang due to API issues
Cascading timeouts in multi-agent scenarios aren't well-handled
CancellationToken propagation works but lacks timeout metadata
Evidence from Codebase:

```
// src/services/MultiAgentOrchestrator.cs:65-72
// Had to implement custom timeout configuration
var clientOptions = new Azure.AI.OpenAI.AzureOpenAIClientOptions
{
NetworkTimeout = TimeSpan.FromSeconds(60) // Manual workaround
};

// Each agent call takes 20-40s with tools
// No framework-level timeout orchestration
```

Recommended Changes:

Add Timeout property to AgentRunOptions
Throw AgentTimeoutException with partial results when timeout occurs
Provide built-in timeout policies for common scenarios
Support graceful degradation when sub-agents timeout
Example Desired API:

```
// Per-invocation timeout
var result = await agent.RunAsync(
prompt,
options: new AgentRunOptions
{
Timeout = TimeSpan.FromSeconds(30),
TimeoutBehavior = TimeoutBehavior.ReturnPartial // or ThrowException
});

// Agent builder timeout policy
var agent = chatClient.CreateAIAgent(
name: "SlowAgent",
instructions: "...",
options: new AgentOptions
{
DefaultTimeout = TimeSpan.FromSeconds(45)
});
```