This task is for tracking the work in the Compatibility (base) layer of the PCS.

This layer is focused on:

1. Removing editing focused markup not needed for reading clients
2. Adding additional markup to HTML by using heuristics in order to identify elements for structured data access
3. Aggregating CSS files and efficiently linking to these files from the HTML

Please see the subtask for the specific API implementations that make up this layer and see the parent ticket for details at the system level.