Refactor: dedupe input reads, material-property guards, button hooks

Extract byte-identical duplicated code into shared helpers (behaviour-neutral):
- New InputUtil.cs: single source for mouse-delta/scroll/cursor-lock, modifier
  and mouse-button reads, previously copied verbatim across camera controllers,
  MeshPainter, FirstPersonMode and PlayerCharacterController.
- GetMatFloat/SetMatFloat replace the 12x material-instance + HasProperty guard
  pattern for the camo/height float properties.
- Route two inline button hooks through the existing Hook() helper.

Bespoke variants deliberately kept local (FreeCam SprintHeld = LeftShift only,
MeshPainter.TryGetMouse with out-params).

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

Assets/Scripts/PlayerCharacterController.cs

@@ -775,12 +775,12 @@ public class PlayerCharacterController : MonoBehaviour
         // offset eases back to zero while moving and never detaches. On a WALL the turn is a held
         // yaw offset from the wall normal (kept until leaving); on a CEILING the body is free like
         // on the ground, so the drag rotates the transform directly. Either drag pauses the orbit.
-        bool offsetDrag = found && IsLeftMouseHeld();
-        bool yawDrag = found && IsRightMouseHeld();
+        bool offsetDrag = found && InputUtil.LeftMouseHeld();
+        bool yawDrag = found && InputUtil.RightMouseHeld();
         if (offsetDrag || yawDrag)
         {
             _offsetDragging = true;
-            Vector2 drag = ReadMouseDelta();
+            Vector2 drag = InputUtil.ReadMouseDelta();
             if (offsetDrag)
                 _wallOffset = Mathf.Clamp(_wallOffset - drag.y * wallOffsetSensitivity, -wallMaxInset, wallMaxOffset);
             if (yawDrag)
@@ -948,14 +948,14 @@ public class PlayerCharacterController : MonoBehaviour
     {
         _offsetDragging = false;
         
-        bool offsetDrag = IsLeftMouseHeld();
-        bool yawDrag = IsRightMouseHeld();
+        bool offsetDrag = InputUtil.LeftMouseHeld();
+        bool yawDrag = InputUtil.RightMouseHeld();
         bool hasMoveInput = (h * h + v * v) > 1e-4f;
 
         if (offsetDrag || yawDrag)
         {
             _offsetDragging = true;
-            Vector2 drag = ReadMouseDelta();
+            Vector2 drag = InputUtil.ReadMouseDelta();
             if (offsetDrag)
                 _groundOffset = Mathf.Clamp(
                     _groundOffset + drag.y * wallOffsetSensitivity, -wallMaxInset, wallMaxOffset);
@@ -1245,33 +1245,6 @@ public class PlayerCharacterController : MonoBehaviour
         _mantleTimer = 0f;
     }
 
-    bool IsLeftMouseHeld()
-    {
-#if ENABLE_INPUT_SYSTEM
-        return Mouse.current != null && Mouse.current.leftButton.isPressed;
-#else
-        return Input.GetMouseButton(0);
-#endif
-    }
-
-    bool IsRightMouseHeld()
-    {
-#if ENABLE_INPUT_SYSTEM
-        return Mouse.current != null && Mouse.current.rightButton.isPressed;
-#else
-        return Input.GetMouseButton(1);
-#endif
-    }
-
-    Vector2 ReadMouseDelta()
-    {
-#if ENABLE_INPUT_SYSTEM
-        return Mouse.current != null ? Mouse.current.delta.ReadValue() : Vector2.zero;
-#else
-        return new Vector2(Input.GetAxisRaw("Mouse X"), Input.GetAxisRaw("Mouse Y")) * 10f;
-#endif
-    }
-
     /// <summary>
     /// Collects contact normals during Move: wall/ceiling contacts feed the
     /// wall-climb detector, the flattest upward contact becomes the ground normal.