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/FreeCamController.cs

@@ -91,11 +91,11 @@ public class FreeCamController : MonoBehaviour
         {
             IgnorePlayerCollision();
             SyncToCurrentView();
-            SetCursorLocked(true);
+            InputUtil.SetCursorLocked(true);
         }
         else
         {
-            SetCursorLocked(false);
+            InputUtil.SetCursorLocked(false);
         }
 
         enabled = active;
@@ -109,7 +109,7 @@ public class FreeCamController : MonoBehaviour
 
     void LookTick()
     {
-        Vector2 delta = ReadMouseDelta() * MouseSensitivity.Multiplier;
+        Vector2 delta = InputUtil.ReadMouseDelta() * MouseSensitivity.Multiplier;
         _yaw += delta.x * horizontalSensitivity;
         float vs = verticalSensitivity * (invertY ? 1f : -1f);
         _pitch = Mathf.Clamp(_pitch + delta.y * vs, -maxPitch, maxPitch);
@@ -222,18 +222,4 @@ public class FreeCamController : MonoBehaviour
 #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
-    }
-
-    static void SetCursorLocked(bool locked)
-    {
-        Cursor.lockState = locked ? CursorLockMode.Locked : CursorLockMode.None;
-        Cursor.visible = !locked;
-    }
 }