Currently, MetaItems are stored outside the main linear data structure, in a separate meta linear data structure. This complicates the processing of linear data: transaction processing, rebasing, serialization/deserialization etc, and makes it harder to reason about document correctness. Instead:

• Store metadata as block nodes in the main data list
• On conversion from HTML, hoist metadata found in a content position to a legal structural position
• On conversion back to HTML, roundtrip metadata hoisted from unmodified content branch nodes back into the original content position
• When deleting across metadata (e.g. <p>foo[-</p><meta/><p>-]bar</p>), hoist metadata to a legal structural position as necessary