Replace auto paint persistence with a named painting library

Persistence rework:
- Drop auto-load on setup and auto-save on teardown; the painter now always
  seeds fresh from the material.
- Named slots under MeshPaint/Saved/<name>.paint via the existing CHMP
  machinery: SavePaintAs / LoadPaintByName / DeletePaint / ListSavedPaintings /
  PaintExists. Slot files carry the display name in the header.
- Remove the obsolete persistence partials (PlayerCharacterController,
  PlayerPoseController, ThirdPersonOrbitInput) and their references.

Paintings HUD panel:
- Authored Panel_Paintings + Save/Load/Delete dialogs into PaintHudPanel.prefab
  (TMP throughout); PaintHud.Library.cs is now a pure binder that clones the
  entry template per slot.
- Save dialog blocks empty/existing names; Load and Delete confirm first.
- Fix dialog z-order: open dialogs SetAsLastSibling so a dragged panel can no
  longer cover them.
- Lib_ListContent horizontal offsets corrected to 0 (was clipping entry labels
  out of the masked viewport).

Multiplayer:
- Loading a painting re-syncs to all peers via the snapshot broadcast path
  (BroadcastLoadedPaint), covering later late-joiners for free.

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

Assets/Scripts/PaintHud.cs

@@ -117,6 +117,9 @@ public partial class PaintHud : MonoBehaviour
             _panel = go;
         }
 
+        // The paint library now lives inside the authored layout prefab; bind its widgets like the brush panel.
+        BindLibrary(_panel ? _panel.transform : null);
+
         // Bind to a painter as soon as one exists. With networked spawn-on-connect there is none
         // at scene start; BindLocalPlayer then raises PainterChanged when the local avatar spawns
         // and OnPainterChanged wires the widgets. In a non-networked scene the painter is already
@@ -155,6 +158,8 @@ public partial class PaintHud : MonoBehaviour
 
         // Restore the saved panel positions + widget values now that the painter exists.
         RestoreHudState();
+
+        UpdateButtonStates(); // enable Save now that a painter is bound
     }
 
     private void OnDestroy()
@@ -165,7 +170,13 @@ public partial class PaintHud : MonoBehaviour
 
     private void OnModeChanged(GameMode mode)
     {
-        if (_panel) _panel.SetActive(mode is PaintMode);
+        bool paint = mode is PaintMode;
+        if (_panel) _panel.SetActive(paint); // toggles the brush panels and the library panel together
+        if (paint)
+        {
+            if (_libraryBound) RefreshList(); // pick up slots saved/changed since last shown
+        }
+        else HideDialogs();
     }
 
     private static Font LoadFont()