SimulationRun.Create.Request: add deployment so Cloud simulations can pin AgentDispatch

[rdysell]

Summary

SimulationRun.Create.Request in protobufs/livekit_agent_simulation.proto has no deployment field. Cloud simulations that target a live agent (agent_name) therefore cannot select a non-production deployment. Omitted AgentDispatch deployment defaults to production.

CreateAgentDispatchRequest.deployment already exists. Please add the same field to the simulation create request and have the Cloud simulation service pass it through when dispatching the agent job.

Companion CLI issue: livekit/livekit-cli#965

Required protocol change

Add string deployment = …; to SimulationRun.Create.Request (next available field after ci = 13). Empty/unset remains production, matching AgentDispatch.

Safety motivation

Projects that share one Cloud agent name across production + staging + dev cannot run staging simulations safely until this field exists and is honored end-to-end (CLI → SimulationRun create → AgentDispatch).

Verified against @livekit/protocol@1.51.0 (94a0a8d): create request fields are project_id, agent_name, num_simulations, region, scenario_group, concurrency, mode, audio impairments, ci — no deployment.

[rdysell]

Opened #1780 — adds deployment on SimulationRun.Create.Request (field 14), SimulationRun (field 23), and SimulationDispatch (field 5). Empty/unset stays production.

Companion CLI: livekit/livekit-cli#966

The pin is not complete until the Cloud simulation service copies create deployment onto CreateAgentDispatchRequest.deployment so the simulated user waits in the same room as the pinned worker.