Replace an assistant revision's tool-input defaults

Full-replace write body for a revision's keyed tool-input defaults.

tools is the whole keyed map {tool_key: {field: {value, type}}}; null or {} clears all configured defaults for the revision (the setter writes SQL NULL). extra="forbid" rejects stray top-level keys; the inner InputArgConfig tolerates the legacy flat {field: value} shape.

GET response for an agent/workflow revision's keyed tool-input defaults.