assistant_tools: Disallow extra tool parameters by default (#32081)

This prevents models from hallucinating tool parameters.


Release Notes:

- Prevent models from hallucinating tool parameters

crates/assistant_tools/src/assistant_tools.rs

@@ -126,6 +126,7 @@ mod tests {
                     }
                 },
                 "required": ["location"],
+                "additionalProperties": false
             })
         );
     }