Module assembling 

Assembling module

The assembling stage processes parsed AST nodes to attach metadata and perform
post-parsing transformations. Unlike the parsing stage which converts tokens to AST,
assembling stages operate on the AST itself.

The builder returns the root session tree, so assembling first wraps it in a
[`Document`](crate::lex::ast::Document). Annotations, which are metadata, are always
attached to AST nodes so they can be very targeted. Only with the full document in
place can we attach annotations to their correct target nodes.

This is harder than it seems. Keeping Lex ethos of not enforcing structure, this needs
to deal with several ambiguous cases, including some complex logic for calculating
"human understanding" distance between elements.

Current stages:

- `attach_root`: Wraps the built session tree in a [`Document`].
- `attach_annotations`: Attaches annotations from content to AST nodes as metadata.
  See [attach_annotations](stages::attach_annotations) for details.

Note on Document Title:
The document title is extracted during the AST building phase (in `AstTreeBuilder`),
just before the assembling stages begin. It promotes the first paragraph (if followed
by blank lines) to be the document title.

Re-exports

pub use stages::AttachAnnotations;

pub use stages::AttachRoot;

Modules

stages

Individual assembling stages