v0.79.16

Fixed

• The subagent tool's parameter schema now requires one complete mode (agent + task, a non-empty tasks array, or a non-empty chain array) via a schema-level anyOf. Every property was optional before, so a call naming an agent with no task validated and reached the tool, which answered with plain text; models re-issued the identical call indefinitely. With the constraint in the schema, models fill in the task (GLM-5.3: 10 of 10 probes, from 2 of 9), and any call that still misses it is rejected by the agent loop's argument validation with the missing field named. The tool's own invalid-parameter paths also return isError: true (#57).