Setting `LargeOutput` but if subagent started, it won't inherit the LargeOutput but use the operating system's default tmp directory

When using the copilot sdk, we want to specify the LargeOutput dir to limit the large output from Tools be saved to specified directory. It works for the main agent, but sometimes subagents are launched, and the subagents will also call MCP Tools, whose large output will be saved to /tmp in Linux.

This is not ideal, because we want all large output to be saved to the specified directory. Our read tools are not allowed to read any directory in the operainng system, if the large output is saved to the default tmp dir (like /tmp in Linux), some customed defined read tools will fail since we only allow them to read specific directory

No file or test is named. Start by tracing how LargeOutput is propagated from the main agent to launched subagents and their MCP tool calls. Done means large output from both the main agent and subagents is saved in the specified directory rather than the operating system's default temporary directory.

Written by the indexing model from the issue text.