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/InputUtil.cs

@@ -0,0 +1,107 @@
+using UnityEngine;
+#if ENABLE_INPUT_SYSTEM
+using UnityEngine.InputSystem;
+#endif
+
+/// <summary>
+/// Shared low-level input reads that were previously copy-pasted verbatim across the camera rigs
+/// (<see cref="FirstPersonController"/>, <see cref="FreeCamController"/>,
+/// <see cref="ThirdPersonOrbitInput"/>), the paint controller and the first-person shoot mode. Each
+/// method preserves its original per-backend behaviour (new Input System when present, legacy Input
+/// Manager otherwise). Sensitivity scaling stays at the call sites.
+/// </summary>
+public static class InputUtil
+{
+    /// <summary>Raw mouse delta this frame (pixels); the legacy path scales GetAxisRaw by 10 to match.</summary>
+    public static 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>Raw mouse-wheel delta this frame (usually only its sign is used).</summary>
+    public static float ReadScroll()
+    {
+#if ENABLE_INPUT_SYSTEM
+        if (Mouse.current != null) return Mouse.current.scroll.ReadValue().y;
+#endif
+#if ENABLE_LEGACY_INPUT_MANAGER
+        return Input.GetAxis("Mouse ScrollWheel");
+#else
+        return 0f;
+#endif
+    }
+
+    /// <summary>Locks+hides or frees+shows the hardware cursor.</summary>
+    public static void SetCursorLocked(bool locked)
+    {
+        Cursor.lockState = locked ? CursorLockMode.Locked : CursorLockMode.None;
+        Cursor.visible = !locked;
+    }
+
+    public static bool ShiftHeld()
+    {
+#if ENABLE_INPUT_SYSTEM
+        var kb = Keyboard.current;
+        if (kb != null) return kb.leftShiftKey.isPressed || kb.rightShiftKey.isPressed;
+#endif
+#if ENABLE_LEGACY_INPUT_MANAGER
+        return Input.GetKey(KeyCode.LeftShift) || Input.GetKey(KeyCode.RightShift);
+#else
+        return false;
+#endif
+    }
+
+    public static bool CtrlHeld()
+    {
+#if ENABLE_INPUT_SYSTEM
+        var kb = Keyboard.current;
+        if (kb != null) return kb.leftCtrlKey.isPressed || kb.rightCtrlKey.isPressed;
+#endif
+#if ENABLE_LEGACY_INPUT_MANAGER
+        return Input.GetKey(KeyCode.LeftControl) || Input.GetKey(KeyCode.RightControl);
+#else
+        return false;
+#endif
+    }
+
+    public static bool LeftMouseHeld()
+    {
+#if ENABLE_INPUT_SYSTEM
+        return Mouse.current != null && Mouse.current.leftButton.isPressed;
+#else
+        return Input.GetMouseButton(0);
+#endif
+    }
+
+    public static bool RightMouseHeld()
+    {
+#if ENABLE_INPUT_SYSTEM
+        return Mouse.current != null && Mouse.current.rightButton.isPressed;
+#else
+        return Input.GetMouseButton(1);
+#endif
+    }
+
+    public static bool MiddleMouseHeld()
+    {
+#if ENABLE_INPUT_SYSTEM
+        return Mouse.current != null && Mouse.current.middleButton.isPressed;
+#else
+        return Input.GetMouseButton(2);
+#endif
+    }
+
+    /// <summary>Left mouse button pressed on this exact frame (edge, not held).</summary>
+    public static bool LeftClickedThisFrame()
+    {
+#if ENABLE_INPUT_SYSTEM
+        return Mouse.current != null && Mouse.current.leftButton.wasPressedThisFrame;
+#else
+        return Input.GetMouseButtonDown(0);
+#endif
+    }
+}