Lifted the Phase 29 fog draw sequence out of `setVisibilityFog`
into a pure `fogPaintOps` helper that returns an ordered list of
fill operations (one fog rect, then one background-coloured
circle per visibility entry). The renderer now dispatches each op
straight onto a Pixi `Graphics`; the indirection lets the layered-
overpaint contract be tested without booting Pixi.
`tests/fog-paint-ops.test.ts` covers: empty input → no ops; single
circle → fog rect + bg circle in that order; multiple circles → N
bg circles after the fog rect; overlapping circles emitted
independently (the rendering order unions them); zero / negative
world dimensions → no ops.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Ilia Denisov