Changes in preparation for #8238 features.
# Important Notes
Changed edit APIs:
- **`graph.astModule` is deprecated.** It will be removed in my next PR.
- Prefer `graph.edit` to start and commit an edit.
- Use `graph.startEdit` / `graph.commitEdit` if the edit can't be confined to one scope.
- Synchronize Y.Js clients by AST (implements #8237).
- Before committing an edit, insert any parentheses-nodes needed for the concrete syntax to reflect tree structure (fixes#8884).
- Move `externalId` and all node metadata into a Y.Map owned by each `Ast`. This allows including metadata changes in an edit, enables Y.Js merging of changes to different metadata fields, and will enable the use of Y.Js objects in metadata. (Implements #8804.)
### Important Notes
- Metadata is now set and retrieved through accessors on the `Ast` objects.
- Since some metadata edits need to take effect in real time (e.g. node dragging), new lower-overhead APIs (`commitDirect`, `skipTreeRepair`) are provided for careful use in certain cases.
- The client is now bundled as ESM.
- The build script cleans up git-untracked generated files in an outdated location, which fixes lint errors related to `src/generated` that may occur when switching branches.
