build_12 and build_15 rendered mean 0 at every instant of a PLAYING timeline,
and verify-screen scored both OK -- two renderers sharing implied_layer_key,
comparing nothing against nothing.
Implements the constraint as a post-pass over ui_layout::derived_paint_order,
with both of the Decoder's limits copied verbatim: layerless elements only (a
sprite's element alpha says nothing about its texture's coverage) and NOT a
name heuristic (palogo_eff0 is named like an overlay and paints first).
Both controls reproduce: palogo_eff0 forced first, pteff00 still last on all
four title screens at exactly 2 opaque instants. Splashes unmoved against the
oracle at 0.01%.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF
1e06ad2e8e