isBuilderIterator

True for a cross-tick builder — ours, or the stdlib's when a snippet fully-qualified past the shadow — and false for listOf(...).iterator() and friends, whose value would otherwise be driven away as a generator and returned as "(no output)".

McpScope by is: the value comes from the snippet and the test is here, so the two have to agree on the class — they do, repl.* being delegated to the game loader from both sides. SequenceScope by NAME, not is: that one is kotlin.*, so in SPLIT the snippet's copy and ours are different classes and is would answer false for every builder.