Adds __callable__ to the Object global dict: zero args returns {}, one-arg
returns the arg (which mirrors spec ToObject for non-null/undefined). This
unblocks many test262 tests that write 'new Object(true)' or 'Object(5)'
— they were failing with 'Not callable: {:entries ...}' because Object
was a plain dict with no call protocol.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>