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.

ui/docs/renderer.md

@@ -292,20 +292,25 @@ the set from the per-game `MapToggles` rune + the planet-cascade
 rule and pushes it on every effect run; toggling a checkbox
 flips visibility within one frame without a Pixi remount.
 
-## Visibility fog
+## Visible-hyperspace overlay (the "fog")
 
 `RendererHandle.setVisibilityFog(circles)` draws (or removes) the
-Phase 29 fog overlay. Each entry describes a circle around a
-LOCAL planet where the player has scanner / visibility coverage:
+Phase 29 fog overlay used to highlight the player's visible
+hyperspace. Each entry describes a circle around a LOCAL planet
+where the player has scanner / visibility coverage:
 
 - An empty list destroys the existing fog Graphics.
 - A non-empty list creates one fog `Graphics` per torus copy.
-  Each fills the world rectangle with `FOG_COLOR` (two shades
-  lighter than the dark theme background) and "cuts" every
-  circle out of it via Pixi v8's `Graphics.cut()` path operator,
-  so overlapping circles compose into a union hole (no
-  even-odd-fill quirks). The fog is inserted at the bottom of
-  each copy's z-order so primitives paint on top.
+  Each draws a world-sized rectangle filled with `FOG_COLOR` (two
+  shades lighter than the dark theme background), then paints an
+  opaque background-coloured circle on top for every visibility
+  circle. The overpaint order naturally unions overlapping circles
+  — earlier iterations used Pixi v8's `Graphics.cut()` to subtract
+  holes, but `cut()` produces incorrect unions for multiple
+  overlapping holes; layered repainting trades one extra fill per
+  circle for a predictable, geometry-free union.
+- The fog is inserted at the bottom of each copy's z-order so
+  primitives paint on top.
 - The fog never participates in hit-test. Planet glyphs sit on
   top of fog, so clicks on visible planets work unchanged.
 - Wrap mode is honoured for free — `applyMode` hides every
@@ -313,7 +318,7 @@ LOCAL planet where the player has scanner / visibility coverage:
   behaviour because the fog Graphics is a child of each copy.
 
 The map view recomputes the fog input only when the report or the
-fog toggle changes — per-frame cost stays at zero.
+`visibleHyperspace` toggle changes — per-frame cost stays at zero.
 
 ## Debug surface
 
@@ -334,9 +339,9 @@ state without scraping pixels:
 - `getMapCamera()` returns the current camera + viewport +
   canvas-origin snapshot, used by Phase 29 e2e specs to assert
   camera preservation across wrap-mode flips.
-- `getMapFog()` returns the most recent visibility-fog input
+- `getMapFog()` returns the most recent fog input
   (the list of circles last passed to `setVisibilityFog`).
-  Empty when the fog toggle is off.
+  Empty when the `visibleHyperspace` toggle is off.
 
 The active map view registers providers on mount via
 `registerMapPrimitivesProvider` / `registerMapPickStateProvider`