Icon toolbar and resizable browser lists in material editor; mute debug logs

Toolbar: every action is now an icon button (tooltip carries the label,
text fallback with no icon set) via a local iconBtn helper matching the
StageEditor/Timeline convention — Create Material, Presets, Create + Bind,
Bind Current. Icons fill the standard button height (GetFrameHeight, zero
frame padding) so the row stays uniform.

Browser: the materials list and the create-node list are now split by a
draggable HorizontalSplitter (sibling to the column VerticalSplitter)
instead of a fixed 45% / separator; m_browserListRatio holds the list's
share (clamped 0.15-0.85). Create-node entries get a per-category glyph
(Material/Texture/Geometry/Light/Utility) sized to the text line height.

Silence the temporary node-editor drag-regression tracing: the
[NodeGraph] event-trace block is #if 0'd, its PersistNodePosition logs
commented, and the [ed] g_AxNodeEditorDebugLog hook install is commented
out (the vendored editor's dumps are guarded on that hook).

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

src/ui/MaterialEditorPanel.h

@@ -157,6 +157,11 @@ private:
     float m_browserWidth = 220.0f;
     float m_previewWidth = 320.0f;
 
+    /// Fraction of the browser column's height given to the materials list;
+    /// the create-node list takes the rest. User-adjustable via the horizontal
+    /// splitter between them.
+    float m_browserListRatio = 0.45f;
+
     /// Search text of the browser's persistent create-node list.
     char m_browserNodeSearchBuf[128] = "";
     /// Shader id clicked in the browser's create-node list; created at the