Trim comments and use implicit null checks for Unity objects

Reduce comments to non-obvious "why" notes and convert UnityEngine.Object
null checks to implicit bool (if (obj) / if (!obj)). Input System devices
(Mouse.current, Keyboard.current) and plain arrays keep explicit != null.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scripts/GameMode.cs

@@ -1,29 +1,24 @@
 /// <summary>
-/// Base class for a high-level game mode (state) handled by
-/// <see cref="GameModeManager"/>. A mode configures the relevant scene systems
-/// when it becomes active (<see cref="Enter"/>), can clean up when it is left
-/// (<see cref="Exit"/>) and may run per-frame logic in <see cref="Tick"/>.
-///
-/// Modes are plain C# classes (not MonoBehaviours). To add a new mode, derive
-/// from this class and register an instance in GameModeManager.BuildModes().
+/// Base class for a high-level game mode handled by <see cref="GameModeManager"/>.
+/// Modes are plain C# classes (not MonoBehaviours); Enter/Exit/Tick are driven
+/// manually by the manager. Derive from this and register an instance in
+/// GameModeManager.BuildModes().
 /// </summary>
 public abstract class GameMode
 {
-    /// <summary>The owning manager, providing access to the controlled systems.</summary>
     protected GameModeManager Manager { get; private set; }
 
-    /// <summary>Human-readable name (shown in logs / debug UI).</summary>
+    /// <summary>Human-readable name (shown in logs).</summary>
     public abstract string DisplayName { get; }
 
-    /// <summary>Wires the mode to its manager. Called once during registration.</summary>
     internal void Bind(GameModeManager manager) => Manager = manager;
 
-    /// <summary>Called once when this mode becomes the active mode.</summary>
+    /// <summary>Called once when this mode becomes active.</summary>
     public virtual void Enter() { }
 
-    /// <summary>Called once when this mode stops being the active mode.</summary>
+    /// <summary>Called once when this mode stops being active.</summary>
     public virtual void Exit() { }
 
-    /// <summary>Called every frame while this mode is the active mode.</summary>
+    /// <summary>Called every frame while this mode is active.</summary>
     public virtual void Tick() { }
 }