Core data model

The pure-data shapes noggin is built on. The JSON schema validates them, the serializers convert them to/from YAML or JSON, providers load and save them, and every verb-returned view is derived from them.

• NogginDocument — the top-level shape. What the file / localstorage / http providers read and write.
• Item and Note — a single tree entry plus its append-only note log.
• View shapes — the read-side projections verbs return: ItemView, ViewNode, CurrentTreeView, DeletedItem.
• Placement — the "where does the new / moved item go" spec (before / after / into an anchor).
• Type aliases — ItemKey, ItemPath, IsoTimestamp. Opaque string types the rest of the API references.

Immutability

All accessors on a live Noggin return deep-frozen values — the same Item[] reference across two noggin.items reads (until the next mutation) so subscribers can memoise on identity. Consumers must not mutate the values they receive; the freeze is enforced, but the pattern is a design rule regardless.