Refactor Assets/Scripts: trim restating comments, minor structure cleanups

Sweep over 48 files (Editor/ excluded): remove comments that restate the
code, condense class summaries, fix three stale doc statements
(HsvColorPicker alpha bar, PaintHud layoutPrefab, MasterVolume
FallbackDefault). Inline two single-use wrappers (IsPointerOverUi,
BuildModes), drop an unused using, replace a magic literal with the
existing ParallaxBase constant, and convert ~10 UnityEngine.Object null
checks to the implicit-bool convention. No serialized fields, signatures,
RPC/NetworkVariable names, defaults, or #if blocks touched.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/Scripts/Helper/MasterVolume.cs

@@ -12,7 +12,7 @@ public static class MasterVolume
 
     /// The default is the level currently authored on the mixer (its exposed-parameter value
     /// converted back to linear), so a fresh install starts at the mixer's own setting instead of
-    /// an arbitrary constant. Falls back to FallbackDefault if the mixer/param is unavailable.
+    /// an arbitrary constant. Falls back to 0.5 if the mixer/param is unavailable.
     public static float Default => TryReadMixerLinear(out float linear) ? linear : .5f;
 
     // Must match the exposed parameter name authored on the AudioMixer asset.