i15-1: Map capilary type to standards puck position.

In order to know what to load during background/calibration scans, we need to be able to map between capillary type and a position on the standards puck. Since not all capillary types are on the standards puck, there may need to be some logic to find the best fit on the standards puck.

I think capillary type should always be the same as what's in the experiment but if the exact size isn't there we should go for the closest.

## Acceptance Criteria
- There is a mapping between capillary type and pin number
- This is used to populate robot/unload parameters for background and calibration scans

Start by tracing how background and calibration scans populate robot and unload parameters, then locate the existing capillary and standards-puck representations. Define the capillary-type-to-pin mapping and verify that exact matches and closest available sizes produce the expected parameters for both scan types.

Written by the indexing model from the issue text.