.Net Agents - Consider "global" system instructions for `AgentChat`

[crickman]

When a common set of instructions applies to all agents, it may be efficient to define a "global" system instruction at the chat level that can be merged into each agent's specific instructions.

Source: https://rtigger.ca/2024/10/25/multi-agent-without-group-chat/

Need to consider how this intersects with the Assistant API where the instructions are defined and stored remotely.

[github-actions]

This issue is stale because it has been open for 90 days with no activity.