Make every sprite readable at game size #159

Problem

Some sprites can't be read at game size (1x, 1280×720). The model draws detail at 2x or more, the crush step box-downscales it, and small things turn to mush: pickups, Dexter's face at 27 px, the hero's hands with the chair, rover sensors, the debris. Some of the art is now worse than the direction boards it was drawn from.

Acceptance criteria

• Audit every exported atlas at 1x on the real stage background: a contact sheet per atlas, each frame next to its direction board crop. Mark each sprite readable or not.
• Redraw what fails with gpt-image-2.5-sunburst: briefs ask for game-size readability (clear silhouettes, 1-px outlines where the style master has them, fewer and bigger details), at the factor that gives a clean crush.
• Add a legibility check to the asset system: silhouette contrast against the background, and minimum feature size.
• Compare: before and after side by side in the PR.