Dpm Registry Alias

## Goals

- Define an OCI (or Github) repo with a short alias so adding dependencies is terse and less error prone

## Acceptance Criteria

```
# create a new alias for canton-network
dpm add registry canton-network oci://[ghcr.io/digital-asset/decentralized-canton-sync/](http://ghcr.io/digital-asset/decentralized-canton-sync/)

# add a dar dependency with that alias
dpm add component --data-dependencies @canton-network/splice-amulet:devnet

# add a dar dependency with that alias
dpm add registry digital-asset oci://europe-docker.pkg.dev[/](http://ghcr.io/digital-asset/decentralized-canton-sync/)da-images/public/

# add a dar dependency with that alias
dpm add dar @digital-asset/components/damlc:devnet
```

```
(stretch) support pinning with : shorthand
```

Start by tracing the dpm registry and component/dar command entry points used in the acceptance examples. Check how registry URLs and dependency references are currently parsed, then verify the canton-network and digital-asset alias examples end-to-end, including the stretch component:version shorthand if in scope.

Written by the indexing model from the issue text.