Update & refactor dark mode (#4114)

## Description:

- The renderer no longer knows what "dark mode" is.
`RenderSettings.dayNight.mode` (`"light" | "dark"`) is gone — passes
read neutral values (`lighting.ambient: number`, `lighting.enabled:
boolean`).
- `render-settings.json` holds the light-mode baseline. Dark mode is
just another override layer, applied the same way as graphics settings
(`darkNames`, `classicIcons`, etc.).
- New `src/client/render/gl/RenderOverrides.ts` exposes two in-place
mutators with matching shapes:
- `applyGraphicsOverrides(settings, overrides)` — replaces the old
`generateRenderSettings`
  - `applyDarkModeOverride(settings, isDark)`
- `ClientGameRunner` regenerates the live settings each time the user
setting changes via `deepAssign(live, createRenderSettings())` + the
override chain. No per-slice copy list, no intermediate object — adding
a new override that touches a new section just works.
- Renamed `dayNight` → `lighting`; collapsed `nightAmbient`/`dayAmbient`
into single `ambient`; renamed `enableLightCompositing` → `enabled`.
- Bumped dark-mode ambient from 0.15 → 0.35 so terrain stays readable.

<img width="1250" height="846" alt="Screenshot 2026-06-02 at 11 47
28 AM"
src="https://github.com/user-attachments/assets/b41e8ffb-6011-4ba0-9e1f-c2a21ff90794"
/>

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/client/render/gl/debug/Layout.ts

@@ -2,7 +2,6 @@ import type { RenderSettings } from "../RenderSettings";
 import type { DebugNode } from "./Folder";
 import { folder } from "./Folder";
 import { color } from "./props/Color";
-import { select } from "./props/Select";
 import { slider } from "./props/Slider";
 import { toggle } from "./props/Toggle";
 
@@ -90,30 +89,29 @@ export function buildTree(s: RenderSettings, d: RenderSettings): DebugNode[] {
       slider(s.falloutBloom, "particleFreshScale", d.falloutBloom, 0, 1, 0.01),
     ]),
 
-    folder("Day / Night", [
-      select(s.dayNight, "mode", d.dayNight, ["light", "dark"], "Mode"),
-      slider(s.dayNight, "nightAmbient", d.dayNight, 0, 1, 0.01),
-      slider(s.dayNight, "dayAmbient", d.dayNight, 0, 1, 0.01),
-      slider(s.dayNight, "falloffPower", d.dayNight, 0.5, 5, 0.1),
-      slider(s.dayNight, "falloutLightIntensity", d.dayNight, 0, 20, 0.1),
-      slider(s.dayNight, "falloutLightThreshold", d.dayNight, 0, 0.5, 0.001),
-      slider(s.dayNight, "blurZoomDivisor", d.dayNight, 1, 20, 0.5),
-      slider(s.dayNight, "lightRadiusMultiplier", d.dayNight, 0.1, 5, 0.1),
+    folder("Lighting", [
+      toggle(s.lighting, "enabled", d.lighting),
+      slider(s.lighting, "ambient", d.lighting, 0, 1, 0.01),
+      slider(s.lighting, "falloffPower", d.lighting, 0.5, 5, 0.1),
+      slider(s.lighting, "falloutLightIntensity", d.lighting, 0, 20, 0.1),
+      slider(s.lighting, "falloutLightThreshold", d.lighting, 0, 0.5, 0.001),
+      slider(s.lighting, "blurZoomDivisor", d.lighting, 1, 20, 0.5),
+      slider(s.lighting, "lightRadiusMultiplier", d.lighting, 0.1, 5, 0.1),
       color(
-        s.dayNight,
+        s.lighting,
         "falloutLightR",
         "falloutLightG",
         "falloutLightB",
-        d.dayNight,
+        d.lighting,
         "Fallout Light Color",
       ),
-      slider(s.dayNight, "emberLightIntensity", d.dayNight, 0, 20, 0.1),
+      slider(s.lighting, "emberLightIntensity", d.lighting, 0, 20, 0.1),
       color(
-        s.dayNight,
+        s.lighting,
         "emberLightR",
         "emberLightG",
         "emberLightB",
-        d.dayNight,
+        d.lighting,
         "Ember Light Color",
       ),
     ]),