Standardize Artifact Packaging and Distribution via OCI

## Problem Statement

Currently, Gemara artifacts are distributed inconsistently across different repositories. To achieve an interoperable ecosystem, we need a standardized way to package, sign, and programmatically resolve these artifacts for use in consuming tools.

## Proposed Solution

Adopt OCI Artifacts as the standard packaging format. This allows us to leverage existing container registry infrastructure for versioning, distribution, and signing solutions.

### Success Criteria
* The SDK defines a clear interface for what constitutes a Gemara bundle.
* Downstream tools can programmatically resolve a catalog that depends on external imports by referencing OCI URIs.
* A standard GitHub Action exists to automate the creation of these bundles

### Next Steps
1. [ ] Define the OCI media types and example manifest
2. [ ] Implement `Pack` and `Unpack` interfaces in the Go SDK