[Bug] Plan mode subagents report context limit exceeded on first prompt from main agent

Question

## Bug Description
Plan mode appears to be hitting the context limit immediately when the main agent delegates tasks to subagents. Each subagent returns a `Context limit reached · /compact or /clear to continue` error on the first prompt, before doing any work.

This happens immediately on the first prompt, so it seems like the subagents are starting with an already-full context or inheriting too much context from the main agent.

Environment Info

* Platform: darwin
* Terminal: VS Code
* Versio