Spike: Group control doesn't load until PDF loads

## Feature Request Form
### Problem you are trying to address with this feature

For long PDFs, the document must finish loading before the URL is sent to the service (for annotations to be fetched). If the document is long and/or slow, this could mean that for a minute or more the interface a) appears broken, and b) no annotations are showing (let alone anchored), and c) no new annotations can be created.

### Your solution

Try to separate complete loading from other H processes.

### Add tags - did you add labels?
If this a customer requested feature, make sure to add that label.

No files, tests, or entry points are identified. Start by reviewing the PDF loading and annotation-fetch flow; done means the group control and annotation actions are available before a long PDF finishes loading.

Written by the indexing model from the issue text.