Add Average Conditional Kernel Inducing Points

### What's the new feature?

Subticket of #1104 , add the conditional inducing point algorithm from https://arxiv.org/abs/2504.10139

### What value does this add?

Has been shown to outperform joint methods on conditional downstream tasks.

### Is there an alternative you've considered?

_No response_

### Additional context

_No response_

Start with the parent issue #1104 and read the linked paper describing the conditional inducing point algorithm. The issue names no files, entry points, tests, or concrete acceptance checks; completion would require adding the algorithm and establishing how its conditional downstream performance should be validated.

Written by the indexing model from the issue text.