NinjaSln-labs/dsh-subagent-router

Model-routed subagent delegation for DeepSeek Harness: a `subagent_model` tool with per-call provider/model/max_tokens overrides and a built-in `model: "auto"` routing policy (anchored to the parent's own model by default; task-tier upgrades, failure escalation, auditable reason), plus a `subagent_models` catalog tool. Children no longer need to inherit the parent's model.