fix(ui-map): repaint fog as layered overpaint; rename to visibleHyperspace

The Phase 29 fog overlay rendered as a handful of random arc
segments instead of a clean union of holes around LOCAL planets
— Pixi v8's `Graphics.cut()` does not reliably subtract multiple
overlapping circles from a base path.

Replaced the cut-based approach with a layered overpaint: a
fog-tinted rectangle fills the world, then opaque background-
coloured circles are painted on top for every visibility circle.
The natural rendering order unions overlapping circles for free —
no geometry, no `cut()` quirks, one extra fill per circle.

Renamed the toggle from `visibilityFog` to `visibleHyperspace`
across the store, i18n strings, popover, tests, and docs. The
overlay still implements the visual "fog" effect at the renderer
level (FOG_COLOR, setVisibilityFog, getMapFog); the toggle is
named after the player-facing concept it controls — the portion
of the map that is visible (intelligence/scan coverage) — rather
than the obscured part.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/docs/game-state.md

@@ -121,7 +121,7 @@ with the new mode.
 Phase 29 adds a `mapToggles: MapToggles` rune that drives the
 gear popover in the map view. Every flag defaults to `true` —
 including `unreachablePlanets` (showing every planet by default)
-and `visibilityFog` (the fog overlay on by default). The
+and `visibleHyperspace` (the fog overlay on by default). The
 exhaustive shape lives in `src/lib/game-state.svelte.ts`; the
 gear popover (`src/lib/active-view/map-toggles.svelte`) is a
 thin view of the rune.