v8 boundary: method calls on returned objects

[cs01]

Pragma returns an object with methods. Native caller can't invoke obj.foo().

Ask

• New bridge fn cs_v8_handle_call_method(h, name, n_args, arr) -> handle
• Marshal synth reads declared interface type of returned object, exposes methods as native-callable
• Works alongside v8 boundary: callbacks native→JS #622 object field walking

Est

~300-500 LOC.