feat(highlight): replace the small-player highlight toggle with a strength slider (#4588)

## Description:

Replaces the "Highlight small players" on/off toggle with a **0-500%
Strength slider** controlling the glow's **width** (0 = off, 100% = the
previous default).

- `UserSettings`: `highlightSmallPlayers()`/toggle →
`highlightGlowStrength()`/set, float-backed, clamped to [0, 5].
- `SmallPlayerGlowPass` takes the strength via a setter (pushed by
`ClientGameRunner` on the settings-changed event), so it stays a pure
consumer and the slider still updates live while the settings modal has
the sim paused. Width = a non-linear blur-iteration count; intensity
compensated so wider stays about as bright.
- `MapRenderer` persists the strength across a WebGL context restore.
- `SettingsModal`: the toggle row becomes a range input.

Behavior note: with the toggle gone the glow **defaults ON at 100%**
(old toggle defaulted OFF); can default to 0 (opt-in) if preferred.

## 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

src/client/WebGLFrameBuilder.ts

@@ -14,7 +14,6 @@ import {
 } from "../core/CosmeticSchemas";
 import { decodePatternData } from "../core/PatternDecoder";
 import { PlayerType } from "../core/game/Game";
-import { UserSettings } from "../core/game/UserSettings";
 import { getCachedCosmetics } from "./Cosmetics";
 import { uploadFrameData } from "./render/frame/Upload";
 // Type-only: a value import would pull GPURenderer and its `.glsl?raw` shader
@@ -197,7 +196,6 @@ export class WebGLFrameBuilder {
   }
 
   private readonly highlightSetBuf = new Uint8Array(PALETTE_SIZE);
-  private readonly userSettings = new UserSettings();
   private glowRescanTick = 0;
 
   update(gameView: GameView): void {
@@ -350,8 +348,9 @@ export class WebGLFrameBuilder {
    * Client-only view — toggle it live in the settings.
    */
   private syncSmallPlayerGlow(gameView: GameView): void {
+    // Strength (incl. off at 0) is read live in the glow pass; here we only
+    // decide who qualifies. Skip spawn + the first minute.
     if (
-      !this.userSettings.highlightSmallPlayers() ||
       gameView.inSpawnPhase() ||
       gameView.elapsedGameSeconds() < SMALL_PLAYER_GLOW_GRACE_SECONDS
     ) {