dsh-subagent-concurrency-limit: Limiting DeepSeek Harness Subagent Concurrency

`dsh-subagent-concurrency-limit` is a workflow plugin for DeepSeek Harness (DSH) that limits the concurrent execution of root-level delegations and local subagents within the same process. It uses a FIFO queue and a custom concurrency pool to prevent subagents from exhausting system resources. It supports nested and remote processes but does not limit the root agent, with a default concurrency limit of 2.