Two root causes behind the blank F6 run:
1. project.godot had no display/stretch config (README mandates canvas_items
@ 1920x1080). Added [display] window size + stretch mode/aspect — the
project's canvas foundation, needed by every screen.
2. A root Control run directly (F6) is not sized to the viewport by full-rect
anchors — it collapses to (0,0), clipping the ScrollContainer and hiding all
content. Size the root to the viewport explicitly and track size_changed
(dropping the full-rect anchors, which conflict with setting size directly).
Faithful main-scene run now measures root = scroll = viewport = 1920x1080.
Suite 125/125.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
