v0.87.0

Arrays become first-class typed fields via a required items element
schema, datetime is unified under a single type: datetime accepting the
full YAML-1.1-style timestamp range (FieldType::Date is gone), and object
zero values are now shape-valid. This release tightens schema-load
validation in several places — empty properties maps and deeper array
nesting are now rejected — and consolidates the example/default conformance
checks behind one shared primitive. Documentation now ships from GitHub
Pages instead of Read the Docs.

Breaking changes

These are schema-load cutovers for Quill.yaml authors; full before/after
steps are in docs/migrations/0.86-to-0.87.md.

• Array fields now require an items element schema (#672). Arrays
  previously carried a single untyped Array type; scalar arrays were
  never coerced or validated element-wise and were always annotated
  array<string>. Every array field must now declare items, and schema
  load rejects arrays without it. The bare-properties-on-an-array form
  (the old "typed table") is removed in favor of
  items: { type: object, properties: … }. Migration for a typed table:

  # before
  rows:
    type: array
    properties: { name: { type: string }, qty: { type: integer } }
  # after
  rows:
    type: array
    items:
      type: object
      properties: { name: { type: string }, qty: { type: integer } }

  A scalar array adds items directly, e.g.
  counts: { type: array, items: { type: integer } }. Elements now coerce
  and validate against items (failing at the indexed path, e.g.
  counts[1]), and blueprint annotations reflect the element type
  (array<integer>, array<markdown>, …). Bundled quills and the
  usaf_memo golden schema are migrated.

• FieldType::Date removed; use type: datetime (#679). type: date
  no longer exists. type: datetime now accepts the full range from a bare
  YYYY-MM-DD date through RFC 3339 with offset (seconds optional, T or
  space separator). Datetime values gain calendar validation (e.g. Feb 30
  is now rejected), and JSON Schema output emits format: date-time for
  all datetime fields. The WASM FieldType union drops "date". The
  blueprint hint is now datetime<YYYY-MM-DD[Thh:mm:ss]>.

• Empty properties: {} on an object field is rejected (#678). An
  empty properties map carries no information (the only conforming value is
  {}) and is almost always a mistake. It is now treated like a missing
  properties key and surfaces quill::object_empty_properties.

• Deeper array nesting is rejected (#673). The documented "one level of
  nesting" contract is now enforced in a single recursive pass, closing a
  gap where array<object<array>> and object<array> were silently
  accepted. A typed table row and a typed dictionary may carry scalar
  columns/properties only; deeper shapes fail with
  quill::nested_array_not_supported.

Behavioral changes

• Object zero values are now shape-valid (#677). zero_value returned
  a bare {} for every object field, which failed validation on any object
  with properties (each absent property reported as MustFillUnset), so
  the zero-filled render path broke for object fields. An object with
  properties now recurses, zero-filling each property to its own
  type-empty leaf. {} remains the zero only for the property-less edge
  case.
• example: values are now validated (#680). The conformance check for
  example/default literals recurses into array items and object
  properties and validates datetime format — capabilities the old
  load-time path lacked, so previously-unvalidated example: values are
  now caught.

Documentation & infrastructure

• Docs hosting moved from Read the Docs to GitHub Pages (#671). A new
  docs.yml workflow builds MkDocs (strict build as a PR check) and
  deploys to Pages on a published release; RCs are skipped. .readthedocs.yaml
  is removed and homepage/User Guide links point at the Pages URL.
• Canon + docs: partial documents are first-class citizens (#670). The
  docs and binding READMEs no longer claim Must Fill fields must be supplied
  before shipping. The only hard render gate is well-formedness (values
  coerce, no surviving <must-fill> sentinel); completeness is a hint
  surfaced by the form view. The format-designer/ docs tree is renamed to
  quills/.
• A Migration section overview page was added and wired into the nav (#674).

Internal

• Example/default validation is consolidated behind a single
  validate_schema_literal conformance core shared by quillmark-core
  config loading and the CLI validate command, with author-friendly
  diagnostics preserved (#680).
• Array and markdown handling collapse into recursive passes over the
  schema in both schema-shape validation and the Typst markdown transform
  (#673).
• Doc/comment fixes from the array-items review (#675).