fix(draw_figures): Merge per-figure defaults into plot specs (temporary)

_draw_single_figure() now reads fig_spec['defaults'] and merges
into cascade: top-level < fig_defaults < plot_spec.
Also adds layout=(nrows, ncols) tuple support.

Temporary fix — proper solution is to delegate subplot loop to
dfdraw's _draw_batch_groups and keep only data caching in ADF.
See dfdraw team discussion for architectural simplification.

Author: miranov25

UTILS/dfextensions/AliasDataFrame/AliasDataFrame.py

@@ -10757,8 +10757,18 @@ def _draw_single_figure(
         from dfextensions.dfdraw import DFDraw
 
         plots = fig_spec.get('plots', [])
-        ncols = fig_spec.get('ncols', 2)
-        nrows = (len(plots) + ncols - 1) // ncols
+        
+        # Layout: support explicit (nrows, ncols) or just ncols
+        layout = fig_spec.get('layout')
+        if layout:
+            nrows, ncols = layout
+        else:
+            ncols = fig_spec.get('ncols', 2)
+            nrows = (len(plots) + ncols - 1) // ncols
+        
+        # Merge per-figure defaults into cascade: top-level < fig_defaults < plot_spec
+        fig_defaults = fig_spec.get('defaults', {})
+        effective_defaults = {**defaults, **fig_defaults}
 
         # Calculate figure size
         figsize = fig_spec.get('figsize')
@@ -10794,8 +10804,8 @@ def _draw_single_figure(
             if isinstance(plot_spec, str):
                 plot_spec = {'expr': plot_spec}
 
-            # Merge with defaults (plot-level overrides defaults)
-            merged = {**defaults, **plot_spec}
+            # Merge with defaults (plot-level overrides fig-level overrides top-level)
+            merged = {**effective_defaults, **plot_spec}
             expr = merged.pop('expr')
             plot_type = merged.pop('type', 'auto')
             title = merged.pop('title', None)