Add NoActionBudgetState interface tracking remaining/default/max budget, implement budget system with DEFAULT=3/MAX=8 limits and STAGNATION_REPEAT_LIMIT=2, add setNoActionFollowupBudget/getNoActionBudgetState/resetNoActionFollowupBudget methods, track stagnation via buildNoActionSignature comparing returnValue+logs across turns, block follow-ups when budget exhausted or stagnated and emit brain