feat(matplotlib): implement scatter-marginal (#6124)

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

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

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

**Parent Issue:** #2005

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/25592616567)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

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

@@ -1,60 +1,81 @@
-""" pyplots.ai
+""" anyplot.ai
 scatter-marginal: Scatter Plot with Marginal Distributions
-Library: matplotlib 3.10.8 | Python 3.13.11
-Quality: 91/100 | Created: 2025-12-26
+Library: matplotlib 3.10.9 | Python 3.13.13
+Quality: 89/100 | Updated: 2026-05-09
 """
 
+import os
+
 import matplotlib.pyplot as plt
 import numpy as np
 from matplotlib.gridspec import GridSpec
 
 
+# Theme tokens
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+BRAND = "#009E73"
+
 # Data - correlated bivariate data with realistic pattern
 np.random.seed(42)
 n = 200
 
-# Create correlated data with some structure
-x = np.concatenate(
-    [
-        np.random.normal(30, 8, n // 2),  # First cluster
-        np.random.normal(60, 10, n // 2),  # Second cluster
-    ]
-)
-y = 0.7 * x + np.random.normal(0, 8, n) + 10  # Linear relationship with noise
+# Create correlated data with bimodal structure
+x = np.concatenate([np.random.normal(30, 8, n // 2), np.random.normal(60, 10, n // 2)])
+y = 0.7 * x + np.random.normal(0, 8, n) + 10
 
 # Create figure with GridSpec for layout
-fig = plt.figure(figsize=(16, 9))
+fig = plt.figure(figsize=(16, 9), facecolor=PAGE_BG)
 gs = GridSpec(4, 4, figure=fig, hspace=0.05, wspace=0.05)
 
 # Main scatter plot (lower-left, 3x3)
-ax_main = fig.add_subplot(gs[1:4, 0:3])
-ax_main.scatter(x, y, s=120, alpha=0.65, color="#306998", edgecolors="white", linewidth=0.5)
-ax_main.set_xlabel("X Value", fontsize=20)
-ax_main.set_ylabel("Y Value", fontsize=20)
-ax_main.tick_params(axis="both", labelsize=16)
-ax_main.grid(True, alpha=0.3, linestyle="--")
+ax_main = fig.add_subplot(gs[1:4, 0:3], facecolor=PAGE_BG)
+ax_main.scatter(x, y, s=100, alpha=0.65, color=BRAND, edgecolors=PAGE_BG, linewidth=0.5)
+ax_main.set_xlabel("Feature A", fontsize=20, color=INK)
+ax_main.set_ylabel("Feature B", fontsize=20, color=INK)
+ax_main.tick_params(axis="both", labelsize=16, colors=INK_SOFT)
+ax_main.yaxis.grid(True, alpha=0.10, linewidth=0.8, color=INK)
+for s in ("left", "bottom"):
+    ax_main.spines[s].set_color(INK_SOFT)
+ax_main.spines["top"].set_visible(False)
+ax_main.spines["right"].set_visible(False)
 
 # Top marginal histogram (aligned with main x-axis)
-ax_top = fig.add_subplot(gs[0, 0:3], sharex=ax_main)
-ax_top.hist(x, bins=25, color="#306998", alpha=0.7, edgecolor="white", linewidth=0.8)
-ax_top.tick_params(axis="x", labelbottom=False)
-ax_top.tick_params(axis="y", labelsize=14)
-ax_top.set_ylabel("Count", fontsize=16)
+ax_top = fig.add_subplot(gs[0, 0:3], sharex=ax_main, facecolor=PAGE_BG)
+ax_top.hist(x, bins=25, color=BRAND, alpha=0.5, edgecolor=PAGE_BG, linewidth=0.5)
+ax_top.tick_params(axis="x", labelbottom=False, colors=INK_SOFT)
+ax_top.tick_params(axis="y", labelsize=14, colors=INK_SOFT)
+ax_top.set_ylabel("Count", fontsize=16, color=INK)
 ax_top.spines["top"].set_visible(False)
 ax_top.spines["right"].set_visible(False)
+for s in ("left", "bottom"):
+    ax_top.spines[s].set_color(INK_SOFT)
+ax_top.yaxis.grid(True, alpha=0.10, linewidth=0.8, color=INK)
 
 # Right marginal histogram (aligned with main y-axis)
-ax_right = fig.add_subplot(gs[1:4, 3], sharey=ax_main)
-ax_right.hist(y, bins=25, orientation="horizontal", color="#306998", alpha=0.7, edgecolor="white", linewidth=0.8)
-ax_right.tick_params(axis="y", labelleft=False)
-ax_right.tick_params(axis="x", labelsize=14)
-ax_right.set_xlabel("Count", fontsize=16)
+ax_right = fig.add_subplot(gs[1:4, 3], sharey=ax_main, facecolor=PAGE_BG)
+ax_right.hist(y, bins=25, orientation="horizontal", color=BRAND, alpha=0.5, edgecolor=PAGE_BG, linewidth=0.5)
+ax_right.tick_params(axis="y", labelleft=False, colors=INK_SOFT)
+ax_right.tick_params(axis="x", labelsize=14, colors=INK_SOFT)
+ax_right.set_xlabel("Count", fontsize=16, color=INK)
 ax_right.spines["top"].set_visible(False)
 ax_right.spines["right"].set_visible(False)
+for s in ("left", "bottom"):
+    ax_right.spines[s].set_color(INK_SOFT)
+ax_right.xaxis.grid(True, alpha=0.10, linewidth=0.8, color=INK)
 
-# Title in the top-right corner area
+# Title
 fig.text(
-    0.98, 0.98, "scatter-marginal · matplotlib · pyplots.ai", fontsize=24, ha="right", va="top", fontweight="normal"
+    0.5,
+    0.98,
+    "scatter-marginal · matplotlib · anyplot.ai",
+    fontsize=24,
+    ha="center",
+    va="top",
+    color=INK,
+    fontweight="medium",
 )
 
-plt.savefig("plot.png", dpi=300, bbox_inches="tight", facecolor="white")
+plt.savefig(f"plot-{THEME}.png", dpi=300, bbox_inches="tight", facecolor=PAGE_BG)