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/MeshPainter.cs

@@ -72,23 +72,23 @@ public partial class MeshPainter : MonoBehaviour
     /// </summary>
     public float CamoHalfLambert
     {
-        get => _materialInstance && _materialInstance.HasProperty(HalfLambertId) ? _materialInstance.GetFloat(HalfLambertId) : 0f;
-        set { if (_materialInstance && _materialInstance.HasProperty(HalfLambertId)) _materialInstance.SetFloat(HalfLambertId, value); }
+        get => GetMatFloat(HalfLambertId, 0f);
+        set => SetMatFloat(HalfLambertId, value);
     }
 
     /// <summary>Companion to <see cref="CamoHalfLambert"/>: additive brightness shift (-1..1) of the
     /// flattened diffuse term, so the body tone can be tuned to match the scene.</summary>
     public float CamoHalfLambertBrightness
     {
-        get => _materialInstance && _materialInstance.HasProperty(HalfLambertBrightnessId) ? _materialInstance.GetFloat(HalfLambertBrightnessId) : 0f;
-        set { if (_materialInstance && _materialInstance.HasProperty(HalfLambertBrightnessId)) _materialInstance.SetFloat(HalfLambertBrightnessId, value); }
+        get => GetMatFloat(HalfLambertBrightnessId, 0f);
+        set => SetMatFloat(HalfLambertBrightnessId, value);
     }
 
     /// <summary>Companion to <see cref="CamoHalfLambert"/>: scales down the direct specular highlight.</summary>
     public float CamoSpecularDampen
     {
-        get => _materialInstance && _materialInstance.HasProperty(SpecularDampenId) ? _materialInstance.GetFloat(SpecularDampenId) : 0f;
-        set { if (_materialInstance && _materialInstance.HasProperty(SpecularDampenId)) _materialInstance.SetFloat(SpecularDampenId, value); }
+        get => GetMatFloat(SpecularDampenId, 0f);
+        set => SetMatFloat(SpecularDampenId, value);
     }
 
     /// <summary>
@@ -101,23 +101,23 @@ public partial class MeshPainter : MonoBehaviour
     /// the deepest painted hole. 0 = no darkening (no black spots), 1 = full black at occ=0.</summary>
     public float OcclusionThreshold
     {
-        get => _materialInstance && _materialInstance.HasProperty(OcclusionThresholdId) ? _materialInstance.GetFloat(OcclusionThresholdId) : 0.2f;
-        set { if (_materialInstance && _materialInstance.HasProperty(OcclusionThresholdId)) _materialInstance.SetFloat(OcclusionThresholdId, value); }
+        get => GetMatFloat(OcclusionThresholdId, 0.2f);
+        set => SetMatFloat(OcclusionThresholdId, value);
     }
 
     /// <summary>Multiplier on the painted-height relief NORMAL strength (1 = base, 0 = flat).</summary>
     public float HeightNormalIntensity
     {
-        get => _materialInstance && _materialInstance.HasProperty(HeightNormalIntensityId) ? _materialInstance.GetFloat(HeightNormalIntensityId) : 1.4f;
-        set { if (_materialInstance && _materialInstance.HasProperty(HeightNormalIntensityId)) _materialInstance.SetFloat(HeightNormalIntensityId, value); }
+        get => GetMatFloat(HeightNormalIntensityId, 1.4f);
+        set => SetMatFloat(HeightNormalIntensityId, value);
     }
 
     /// <summary>Multiplier on the painted-height UV PARALLAX amplitude (1 = base <see cref="ParallaxBase"/>,
     /// 0 = no displacement). Backed by the material's _Parallax, so it round-trips like the others.</summary>
     public float ParallaxIntensity
     {
-        get => _materialInstance && _materialInstance.HasProperty(ParallaxId) ? _materialInstance.GetFloat(ParallaxId) / ParallaxBase : 1f;
-        set { if (_materialInstance && _materialInstance.HasProperty(ParallaxId)) _materialInstance.SetFloat(ParallaxId, Mathf.Max(0f, value) * ParallaxBase); }
+        get => GetMatFloat(ParallaxId, ParallaxBase) / ParallaxBase;
+        set => SetMatFloat(ParallaxId, Mathf.Max(0f, value) * ParallaxBase);
     }
 
     /// <summary>Drives the see-through-walls X-ray overlay (see <c>PlayerCamoLit</c>): sets the TARGET for
@@ -1060,6 +1060,15 @@ public partial class MeshPainter : MonoBehaviour
 
     private static float Cross2D(Vector2 a, Vector2 b) => a.x * b.y - a.y * b.x;
 
+    // Guarded material float access: absent instance/property -> the caller's fallback, no write.
+    private float GetMatFloat(int id, float fallback)
+        => _materialInstance && _materialInstance.HasProperty(id) ? _materialInstance.GetFloat(id) : fallback;
+
+    private void SetMatFloat(int id, float value)
+    {
+        if (_materialInstance && _materialInstance.HasProperty(id)) _materialInstance.SetFloat(id, value);
+    }
+
     private bool TryGetMouse(out bool pressed, out Vector2 screenPos)
     {
         pressed = false;
@@ -1096,8 +1105,8 @@ public partial class MeshPainter : MonoBehaviour
     {
         // Momentary pipette: arm on the Shift/Ctrl press (remembering the toggle's state), force it on
         // while held (re-arms after a one-shot pick), and restore the prior state on release.
-        bool shift = ShiftHeld();
-        bool ctrl = CtrlHeld();
+        bool shift = InputUtil.ShiftHeld();
+        bool ctrl = InputUtil.CtrlHeld();
         bool mod = shift || ctrl;
         if (mod && !_pipetteModHeld) _pipetteBeforeMod = pipette;
         if (mod) pipette = true;
@@ -1108,7 +1117,7 @@ public partial class MeshPainter : MonoBehaviour
         // held, so it does not also zoom).
         if (!mod) return;
 
-        float scroll = ReadScroll();
+        float scroll = InputUtil.ReadScroll();
         if (Mathf.Approximately(scroll, 0f)) return;
 
         // Geometric resize: the step scales with the current size, so small brushes change a texel
@@ -1121,44 +1130,6 @@ public partial class MeshPainter : MonoBehaviour
         BrushSizeChanged?.Invoke();
     }
 
-    private 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
-    }
-
-    private 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
-    }
-
-    private 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>True if the pointer is currently over an interactive UI element (raycast target).</summary>
     private static bool IsPointerOverUi()
     {