Is there a generic `downrank` (like the generic `discard`)?

Instead of discarding non-matched sites entirely (which could exclude useful results too), I tried downranking them all with a

```
$downrank
```
statement. This works for the `$discard` instruction, as shown in some of the example goggles and mentioned [here](https://github.com/brave/goggles-quickstart/blob/main/getting-started.md#how-can-i-exclude-any-result-not-matched-by-my-goggle). But based on some experimentation, this doesn't really seem to work when it's the `downrank` instruction being used this way. As far as I can tell, this instruction is just being silently ignored.

Is there a generic `downrank` feature that I'm just not seeing the effect of in my tests? Or is it not implemented? If it's not yet implemented, please consider this a feature request for a catch-all generic `downrank`.

Start with the linked getting-started.md section on excluding unmatched results and review the example goggles referenced there. Compare the observed behavior of generic $discard and $downrank, then identify where their instruction handling is defined. Done means generic downranking has an agreed behavior, is implemented, and is documented with a way to verify it.

Written by the indexing model from the issue text.