Handle multi-line statements in the console

If a student types the following into the console and presses Enter:

if (name === "Pop") {

The console should recognize that it is an incomplete statement, and allow the student to keep typing (with an expanded input area to accommodate the new line).

This seems hard—how do we distinguish between an incomplete multiline statement and a statement that is syntactically invalid for some other reason? Perhaps Esprima or one of our other linters/parsers throws a specific “unexpected end of input” type error that we can rely on.

Start by tracing the console input handling and how its parser or linter reports an unexpected end of input for the example statement. Determine how incomplete input can be distinguished from other syntax errors and how the input area expands for continued lines. Done means the example can continue across lines while genuinely invalid statements still report errors.