feat(letsplot): implement scatter-marginal (#6131)

## Implementation: `scatter-marginal` - python/letsplot

Implements the **python/letsplot** version of `scatter-marginal`.

**File:** `plots/scatter-marginal/implementations/python/letsplot.py`

**Parent Issue:** #2005

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/25592948372)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Markus Neusinger <2921697+MarkusNeusinger@users.noreply.github.com>

Author: github-actions[bot]

plots/scatter-marginal/implementations/python/letsplot.py

@@ -1,9 +1,11 @@
-""" pyplots.ai
+""" anyplot.ai
 scatter-marginal: Scatter Plot with Marginal Distributions
-Library: letsplot 4.8.2 | Python 3.13.11
-Quality: 90/100 | Created: 2025-12-26
+Library: letsplot 4.9.0 | Python 3.13.13
+Quality: 95/100 | Updated: 2026-05-09
 """
 
+import os
+
 import numpy as np
 import pandas as pd
 from lets_plot import *  # noqa: F403
@@ -12,6 +14,16 @@
 
 LetsPlot.setup_html()  # noqa: F405
 
+# Theme tokens
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+
+BRAND = "#009E73"  # Okabe-Ito position 1
+ACCENT = "#D55E00"  # Okabe-Ito position 2
+
 # Data - bivariate data with correlation
 np.random.seed(42)
 n = 200
@@ -24,20 +36,24 @@
 x_min, x_max = df["x"].min() - 0.5, df["x"].max() + 0.5
 y_min, y_max = df["y"].min() - 0.5, df["y"].max() + 0.5
 
-# Main scatter plot with integrated title
+# Main scatter plot
 main_scatter = (
     ggplot(df, aes(x="x", y="y"))  # noqa: F405
-    + geom_point(color="#306998", size=4, alpha=0.65)  # noqa: F405
+    + geom_point(color=BRAND, size=4, alpha=0.65)  # noqa: F405
     + labs(  # noqa: F405
-        x="X Value", y="Y Value", title="scatter-marginal · letsplot · pyplots.ai"
+        x="Measurement A", y="Measurement B", title="scatter-marginal · letsplot · anyplot.ai"
     )
     + scale_x_continuous(limits=[x_min, x_max])  # noqa: F405
     + scale_y_continuous(limits=[y_min, y_max])  # noqa: F405
     + theme_minimal()  # noqa: F405
     + theme(  # noqa: F405
-        plot_title=element_text(size=24),  # noqa: F405
-        axis_title=element_text(size=20),  # noqa: F405
-        axis_text=element_text(size=16),  # noqa: F405
+        plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),  # noqa: F405
+        panel_background=element_rect(fill=PAGE_BG),  # noqa: F405
+        panel_grid_major=element_line(color=INK_SOFT, size=0.2),  # noqa: F405
+        plot_title=element_text(size=24, color=INK),  # noqa: F405
+        axis_title=element_text(size=20, color=INK),  # noqa: F405
+        axis_text=element_text(size=16, color=INK_SOFT),  # noqa: F405
+        axis_line=element_line(color=INK_SOFT),  # noqa: F405
     )
 )
 
@@ -46,19 +62,23 @@
     ggplot(df, aes(x="x"))  # noqa: F405
     + geom_histogram(  # noqa: F405
         aes(y="..density.."),  # noqa: F405
-        fill="#306998",
-        color="white",
-        alpha=0.6,
+        fill=BRAND,
+        color=PAGE_BG,
+        alpha=0.5,
         bins=25,
     )
-    + geom_density(color="#DC2626", size=1.5, alpha=0.8)  # noqa: F405
+    + geom_density(color=ACCENT, size=1.5, alpha=0.8)  # noqa: F405
     + scale_x_continuous(limits=[x_min, x_max])  # noqa: F405
     + theme_minimal()  # noqa: F405
     + theme(  # noqa: F405
+        plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),  # noqa: F405
+        panel_background=element_rect(fill=PAGE_BG),  # noqa: F405
+        panel_grid_major=element_line(color=INK_SOFT, size=0.15),  # noqa: F405
         axis_title=element_blank(),  # noqa: F405
         axis_text_x=element_blank(),  # noqa: F405
         axis_ticks_x=element_blank(),  # noqa: F405
-        axis_text_y=element_text(size=16),  # noqa: F405
+        axis_text_y=element_text(size=14, color=INK_SOFT),  # noqa: F405
+        axis_line_x=element_blank(),  # noqa: F405
     )
 )
 
@@ -67,40 +87,42 @@
     ggplot(df, aes(x="y"))  # noqa: F405
     + geom_histogram(  # noqa: F405
         aes(y="..density.."),  # noqa: F405
-        fill="#306998",
-        color="white",
-        alpha=0.6,
+        fill=BRAND,
+        color=PAGE_BG,
+        alpha=0.5,
         bins=25,
     )
-    + geom_density(color="#DC2626", size=1.5, alpha=0.8)  # noqa: F405
+    + geom_density(color=ACCENT, size=1.5, alpha=0.8)  # noqa: F405
     + coord_flip()  # noqa: F405
     + scale_x_continuous(limits=[y_min, y_max])  # noqa: F405
     + theme_minimal()  # noqa: F405
     + theme(  # noqa: F405
+        plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),  # noqa: F405
+        panel_background=element_rect(fill=PAGE_BG),  # noqa: F405
+        panel_grid_major=element_line(color=INK_SOFT, size=0.15),  # noqa: F405
         axis_title=element_blank(),  # noqa: F405
         axis_text_y=element_blank(),  # noqa: F405
         axis_ticks_y=element_blank(),  # noqa: F405
-        axis_text_x=element_text(size=16),  # noqa: F405
-        plot_margin=[0, 15, 0, 0],  # noqa: F405
+        axis_text_x=element_text(size=14, color=INK_SOFT),  # noqa: F405
+        axis_line_y=element_blank(),  # noqa: F405
     )
 )
 
 # Combine using ggbunch
-# Regions: (x, y, width, height) - relative coordinates
 combined = (
     ggbunch(  # noqa: F405
         [top_hist, main_scatter, right_hist],
         [
-            (0, 0.08, 0.76, 0.20),  # Top histogram (below title space)
-            (0, 0.28, 0.76, 0.72),  # Main scatter plot (with title at top)
-            (0.76, 0.28, 0.24, 0.72),  # Right histogram (wider for tick labels)
+            (0, 0.0, 0.76, 0.18),  # Top histogram
+            (0, 0.18, 0.76, 0.82),  # Main scatter plot
+            (0.76, 0.18, 0.24, 0.82),  # Right histogram (aligned to bottom of main plot)
         ],
     )
     + ggsize(1600, 900)  # noqa: F405
 )
 
 # Save as PNG (scale 3x to get 4800 x 2700 px)
-export_ggsave(combined, filename="plot.png", path=".", scale=3)
+export_ggsave(combined, filename=f"plot-{THEME}.png", path=".", scale=3)
 
 # Save HTML for interactive version
-export_ggsave(combined, filename="plot.html", path=".")
+export_ggsave(combined, filename=f"plot-{THEME}.html", path=".")