Fix in hand interaction

Expected behavior:
- in-hand inventory interactions should be callable from the inventory flow
- the interaction controller method used for in-hand clicks should be accessible for that cross-call
- keep the change focused on the interaction-controller side of the bug

--- Original GitHub issue (auto-fetched) ---
Title: Fix in hand interaction

Body:
<!-- The notes within these arrows are for you but can be deleted. -->

## Summary
The outdated branch used to have in hand interaction working. Fix it.

## Current Behavior

Does not work.

## Expected Behavior

- Pick up a bikehorn
- Click on its sprite in UI when held in hand.
- honk honk.

## Possible Solution

Look at the outdated code and compare with now. the Inventory script is lacking the ClientInteractWithSingleSlot method, which call "InteractInHand". 

## Dependencies

wait for #1257 to be complete
