docs(changelog): release v0.19.0

Rolls the accumulated [Unreleased] section into 0.19.0 and fills the gap
between it and the 146 non-merge commits since v0.18.0. The section as it
stood documented six issues (#891, #892, #923, #927, #928, #936) and had
drifted out of the canonical shape, carrying five separate "### Fixed"
headings and four "### Added" ones interleaved.

Every pre-existing entry is preserved verbatim and reordered into one
Added / Changed / Fixed run. What had no entry at all is the larger half,
and most of it is user-facing: rules as an authorable document type,
expression type checking under `check --references`, skill packs, a FOLDER
clause on CREATE for every doctype, MOVE accepting all thirty-one, List View
specialization templates, IN QUEUE, REST binary bodies and file-document
responses, GraphQL publishing, guest access, @setup/@verify, six model
settings, and XPath rewriting on attribute rename.

The headline names what most of the fixes have in common: a clause or
annotation that parsed, reported success and was then discarded.

make build, make test and make lint pass.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: ako