Safe subset of the #338 drawable memory diet. UIGrid and UIGridView each
embedded an sf::RenderTexture rotationTexture value member paid by every grid,
though only camera-rotated grids ever use it. Made it a unique_ptr allocated on
first rotation, so non-rotating grids (the common case) don't carry it.
Measured per-drawable resident cost (issue_338_drawable_footprint_test.py, 5000
instances): Frame ~551 B, Caption ~1135 B (the embedded sf::Text). At hundreds
of drawables that is tens of KB total, confirming the issue's own note. The
larger render_sprite base-class relocation is therefore DEFERRED -- it would
touch every render path, which the issue explicitly says to avoid, for a payoff
that does not justify the risk. Left open for that remaining part.
Suite 310/310 (rotation tests green through the lazy path).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
