sessionFor method
Activates agentId and returns a session to generate with (bound to
the agent's sequence in multi-sequence mode).
Activation is serialized: concurrent agent requests queue rather than
interleave. This is the SessionProvider behind every registered
agent's chat client; call it directly only when driving sessions
without the Agents Framework.
Implementation
Future<LlamaSession> sessionFor(String agentId) =>
_tasks.run(() => _activateLocked(agentId));