Connecting multiple data nodes to a SineNode frequency input only outputs one pitch

[jayy-d]

It is possible to connect multiple frequency data nodes to a SineNode frequency input. However, only one frequency gets played back. If a SineNode is not meant to be polyphonic, we should only be able to connect a single DataNode to its frequency input.

Example:

[ThatOtherAndrew]

That's a quirk of the half-hearted frontend implementation I did when first learning Svelte :p

Intended behaviour (and what happens in the backend) is that on making a new connection to an input port, the previous connection is dropped. The UI doesn't reflect that until the next refresh.