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/PLAN.md

@@ -3189,7 +3189,10 @@ Artifacts:
     toggles plus a `unreachablePlanets` switch that, when off,
     hides planets beyond `FlightDistance(localPlayerDrive)` of
     every LOCAL planet (torus-aware).
-  - **View** — visibility-fog checkbox + torus / no-wrap radios.
+  - **View** — "visible hyperspace" checkbox + torus / no-wrap
+    radios. The fog overlay is named for the visible part of the
+    map (intelligence/scan area), since that is what the toggle
+    controls from the player's perspective.
 - `RendererHandle.setHiddenPrimitiveIds(ids)` —
   declarative hide set; flips `Graphics.visible` per copy and
   threads the set into `hitTest` so click-through to deeper
@@ -3245,11 +3248,13 @@ Decisions:
    player's `FlightDistance`. Reach is already implicit in the
    reach-aware destination picker (Phase 16+), so the cleaner UX
    is filtering, not adding extra rings.
-2. **Visibility fog overlay**. A separate `visibilityFog` toggle
-   draws a slightly lighter fog over the world outside the union
-   of `VisibilityDistance` circles around LOCAL planets. The fog
-   is a renderer-level concept (Pixi `Graphics.cut()`), not a
-   primitive — it never participates in hit-test.
+2. **Visible-hyperspace overlay**. A separate `visibleHyperspace`
+   toggle draws a slightly lighter fog over the world outside the
+   union of `VisibilityDistance` circles around LOCAL planets. The
+   fog is a renderer-level concept (layered overpaint — fog rect
+   then background-coloured circles on top — instead of Pixi's
+   `Graphics.cut()`, which produced incorrect unions of holes), not
+   a primitive: it never participates in hit-test.
 3. **Per-kind planet toggles + unidentified-group toggle**. The
    spec's original "object visibility" list was extended:
    foreign / uninhabited / unidentified planet kinds and