6615c5f7d0
The old code iterated every IEnumerable, so `output = "hello"` emitted one
item per character (a string is IEnumerable-of-char) and `output = {"a":1}`
emitted the keys as items. Now the script's output is serialized first and
the ValueKind decides: JSON array → per-element items; anything else →
single item. `output = None` remains an empty emission.
New tests cover string, dict, number, and None shapes.