Snapshots pit of success (#3811)

Lots of people are having a bad time with loading/restoring snapshots
and there's a few reasons for that:

- It's not clear how to preserve UI state independently of document
state.
- Loading a snapshot wipes the instance state, which means we almost
always need to
  - update the viewport page bounds
  - refocus the editor
  - preserver some other sneaky properties of the `instance` record

### Change Type

<!-- ❗ Please select a 'Scope' label ❗️ -->

- [x] `sdk` — Changes the tldraw SDK
- [ ] `dotcom` — Changes the tldraw.com web app
- [ ] `docs` — Changes to the documentation, examples, or templates.
- [ ] `vs code` — Changes to the vscode plugin
- [ ] `internal` — Does not affect user-facing stuff

<!-- ❗ Please select a 'Type' label ❗️ -->

- [ ] `bugfix` — Bug fix
- [ ] `feature` — New feature
- [ ] `improvement` — Improving existing features
- [ ] `chore` — Updating dependencies, other boring stuff
- [ ] `galaxy brain` — Architectural changes
- [ ] `tests` — Changes to any test code
- [ ] `tools` — Changes to infrastructure, CI, internal scripts,
debugging tools, etc.
- [ ] `dunno` — I don't know


### Test Plan

1. Add a step-by-step description of how to test your PR here.
2.

- [ ] Unit Tests
- [ ] End to end tests

### Release Notes

- Add a brief release note for your PR here.

packages/editor/src/lib/config/createTLStore.ts

@@ -21,7 +21,7 @@ export type TLStoreOptions = {
 export type TLStoreEventInfo = HistoryEntry<TLRecord>
 
 /**
- * A helper for creating a TLStore. Custom shapes cannot override default shapes.
+ * A helper for creating a TLStore.
  *
  * @param opts - Options for creating the store.
  *