docs: record how rendering probes mislead, and ThreadListView

A session was spent chasing a defect that did not exist, because three
separate rendering probes returned confidently wrong results and each
was believed until contradicted. The specific failure modes are worth
recording, since the next attempt will otherwise rediscover them:
counting lit pixels cannot tell bold from regular in either direction,
viewport()->render() returns blank images in several ordinary
situations, and a "saturated pixel" threshold catches the antialiased
edge of the selection highlight and passes whatever the code does.

The bug that started it was not in the code at all: the desktop's Qt
font was configured Bold in qt6ct, so every row rendered bold and
setBold() changed nothing.

Also records ThreadListView in the architecture diagram, with the three
consequences of painting a row-wide strip in a per-cell view that are
easiest to undo by accident.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions