Function sanitizeForWire

Copy value into JSON-safe form.

• Error becomes {name, message} (no stack: it names viewer internals and a controller cannot act on it).
• Functions and undefined are dropped, as JSON.stringify would.
• NaN / Infinity become null, because that is what they decode as anyway and a silent null is better than a frame that fails to parse.
• Anything past MAX_WIRE_DEPTH becomes null.