2.0.16: feat(rich-editor): add fullscreen button and roomier default height

The TinyMCE editor had a fixed height of 320px and no way to enlarge it,
so long content had to be edited inside a cramped, scrolling box.

Enable the self-hosted `fullscreen` plugin (ships in the build, no
Node/CDN needed - ADR-004 / NFR-AVAIL-001), add its toolbar button, and
raise the default height 320->480. Config-only change to the shared
<x-gp247::rich-editor> component, so every screen using it benefits.

Ref: US-AUI-004, ADR-005, modification 20260730T231015

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>