docs(changelog): finalize v0.14.0 (Mendix 11.12 support + modelsdk parity)

Roll all 115 commits since the initial v0.14.0 draft into the release
section, dated 2026-07-06, and empty [Unreleased]. Refreshes the headline
to reflect the release's real scope: Mendix 11.12 load/build compatibility,
modelsdk-engine read/serialization parity, OData import/publishing
hardening, and expanded Starlark lint + MCP/PED authoring — alongside the
already-documented JavaScript actions, clickable containers, chart widgets,
page-level CSS, and linkbutton.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ako