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/frontend/tests/map-toggles-state.test.ts

@@ -113,7 +113,7 @@ describe("GameStateStore.mapToggles persistence", () => {
 		await a.init({ client: makeFakeClient(3), cache, gameId: GAME_ID });
 		await a.setMapToggle("hyperspaceGroups", false);
 		await a.setMapToggle("battleMarkers", false);
-		await a.setMapToggle("visibilityFog", false);
+		await a.setMapToggle("visibleHyperspace", false);
 		a.dispose();
 
 		listMyGamesSpy.mockResolvedValue([makeGameSummary(3)]);
@@ -121,7 +121,7 @@ describe("GameStateStore.mapToggles persistence", () => {
 		await b.init({ client: makeFakeClient(3), cache, gameId: GAME_ID });
 		expect(b.mapToggles.hyperspaceGroups).toBe(false);
 		expect(b.mapToggles.battleMarkers).toBe(false);
-		expect(b.mapToggles.visibilityFog).toBe(false);
+		expect(b.mapToggles.visibleHyperspace).toBe(false);
 		// Untouched flags retain defaults.
 		expect(b.mapToggles.bombingMarkers).toBe(true);
 		b.dispose();
@@ -141,7 +141,7 @@ describe("GameStateStore.mapToggles persistence", () => {
 		expect(store.mapToggles.hyperspaceGroups).toBe(false);
 		expect(store.mapToggles.battleMarkers).toBe(true);
 		expect(store.mapToggles.bombingMarkers).toBe(true);
-		expect(store.mapToggles.visibilityFog).toBe(true);
+		expect(store.mapToggles.visibleHyperspace).toBe(true);
 		store.dispose();
 	});
 });
@@ -153,7 +153,7 @@ describe("GameStateStore.mapToggles new-turn reset", () => {
 				...DEFAULT_MAP_TOGGLES,
 				hyperspaceGroups: false,
 				battleMarkers: false,
-				visibilityFog: false,
+				visibleHyperspace: false,
 			},
 			lastResetTurn: 4,
 		});