feat(plotly): implement scatter-marginal (#6126)

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

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

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

**Parent Issue:** #2005

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/25592701480)*

---------

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/plotly.py

@@ -1,64 +1,133 @@
-""" pyplots.ai
+""" anyplot.ai
 scatter-marginal: Scatter Plot with Marginal Distributions
-Library: plotly 6.5.0 | Python 3.13.11
-Quality: 92/100 | Created: 2025-12-26
+Library: plotly 6.7.0 | Python 3.13.13
+Quality: 92/100 | Updated: 2026-05-09
 """
 
+import os
+import sys
+
 import numpy as np
-import plotly.express as px
 
 
-# Data - Bivariate normal with correlation
+try:
+    import plotly.graph_objects as go
+except ImportError:
+    __file__ = os.path.abspath(__file__)
+    __dir__ = os.path.dirname(__file__)
+    if __dir__ in sys.path:
+        sys.path.remove(__dir__)
+    import plotly.graph_objects as go
+
+# 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"
+GRID = "rgba(26,26,23,0.10)" if THEME == "light" else "rgba(240,239,232,0.10)"
+BRAND = "#009E73"
+
+# Data - Bivariate normal with correlation (scientific measurement scenario)
 np.random.seed(42)
 n = 200
-x = np.random.randn(n) * 10 + 50
-y = 0.7 * x + np.random.randn(n) * 8 + 15
+# Temperature (°C) and relative humidity (%)
+temperature = np.random.randn(n) * 3.5 + 22
+humidity = 0.65 * temperature + np.random.randn(n) * 6 + 35
 
-# Create scatter plot with marginal histograms
-fig = px.scatter(x=x, y=y, marginal_x="histogram", marginal_y="histogram")
+# Create scatter plot with marginal histograms using go (for full control)
+fig = go.Figure()
 
-# Style main scatter plot
-fig.update_traces(
-    marker={"size": 14, "color": "#306998", "opacity": 0.65, "line": {"width": 1, "color": "#1e4a6e"}},
-    selector={"type": "scatter", "mode": "markers"},
+# Add scatter trace
+fig.add_trace(
+    go.Scatter(
+        x=temperature,
+        y=humidity,
+        mode="markers",
+        marker=dict(size=14, color=BRAND, opacity=0.65, line=dict(width=1, color=PAGE_BG)),
+        name="Measurements",
+        showlegend=False,
+    )
+)
+
+# Add marginal histogram for X (temperature)
+fig.add_trace(
+    go.Histogram(
+        x=temperature,
+        name="Temp Distribution",
+        marker=dict(color=BRAND, opacity=0.6),
+        yaxis="y2",
+        xaxis="x",
+        showlegend=False,
+        nbinsx=25,
+    )
+)
+
+# Add marginal histogram for Y (humidity)
+fig.add_trace(
+    go.Histogram(
+        y=humidity,
+        name="Humidity Distribution",
+        marker=dict(color=BRAND, opacity=0.6),
+        xaxis="x2",
+        yaxis="y",
+        showlegend=False,
+        nbinsy=25,
+        orientation="h",
+    )
 )
 
-# Style marginal histograms
+# Enhanced hover tooltips for better data storytelling
 fig.update_traces(
-    marker={"color": "#306998", "opacity": 0.7, "line": {"width": 1, "color": "#1e4a6e"}},
-    selector={"type": "histogram"},
+    hovertemplate="<b>Measurement</b><br>Temperature: %{x:.1f}°C<br>Humidity: %{y:.1f}%<extra></extra>",
+    selector=dict(mode="markers"),
 )
 
-# Layout for 4800x2700 px
+# Update layout with refined design: spine removal, subtle grid, publication-grade styling
 fig.update_layout(
-    title={
-        "text": "scatter-marginal \u00b7 plotly \u00b7 pyplots.ai",
-        "font": {"size": 32},
-        "x": 0.5,
-        "xanchor": "center",
-    },
-    xaxis={
-        "title": {"text": "X Value", "font": {"size": 24}},
-        "tickfont": {"size": 18},
-        "gridcolor": "rgba(128, 128, 128, 0.3)",
-        "gridwidth": 1,
-    },
-    yaxis={
-        "title": {"text": "Y Value", "font": {"size": 24}},
-        "tickfont": {"size": 18},
-        "gridcolor": "rgba(128, 128, 128, 0.3)",
-        "gridwidth": 1,
-    },
-    xaxis2={"tickfont": {"size": 14}},
-    yaxis2={"tickfont": {"size": 14}},
-    xaxis3={"tickfont": {"size": 14}},
-    yaxis3={"tickfont": {"size": 14}},
-    template="plotly_white",
-    font={"family": "Arial, sans-serif"},
+    title=dict(text="scatter-marginal · plotly · anyplot.ai", font=dict(size=28, color=INK), x=0.5, xanchor="center"),
+    xaxis=dict(
+        domain=[0, 0.85],
+        title=dict(text="Temperature (°C)", font=dict(size=22, color=INK)),
+        tickfont=dict(size=18, color=INK_SOFT),
+        gridcolor=GRID,
+        linecolor=INK_SOFT,
+        showgrid=True,
+        gridwidth=0.5,
+        showline=True,
+        linewidth=1.5,
+        mirror=False,
+        side="bottom",
+    ),
+    yaxis=dict(
+        domain=[0, 0.85],
+        title=dict(text="Relative Humidity (%)", font=dict(size=22, color=INK)),
+        tickfont=dict(size=18, color=INK_SOFT),
+        gridcolor=GRID,
+        linecolor=INK_SOFT,
+        showgrid=True,
+        gridwidth=0.5,
+        showline=True,
+        linewidth=1.5,
+        mirror=False,
+        side="left",
+    ),
+    xaxis2=dict(
+        domain=[0.85, 1], showticklabels=False, gridcolor=GRID, linecolor=INK_SOFT, showgrid=False, showline=False
+    ),
+    yaxis2=dict(
+        domain=[0.85, 1], showticklabels=False, gridcolor=GRID, linecolor=INK_SOFT, showgrid=False, showline=False
+    ),
+    paper_bgcolor=PAGE_BG,
+    plot_bgcolor=PAGE_BG,
+    font=dict(family="Arial, sans-serif", color=INK),
     showlegend=False,
-    margin={"l": 100, "r": 100, "t": 120, "b": 100},
+    margin=dict(l=120, r=80, t=100, b=100),
+    height=900,
+    width=1600,
+    hovermode="closest",
 )
 
 # Save
-fig.write_image("plot.png", width=1600, height=900, scale=3)
-fig.write_html("plot.html", include_plotlyjs="cdn")
+fig.write_image(f"plot-{THEME}.png", width=1600, height=900, scale=3)
+fig.write_html(f"plot-{THEME}.html", include_plotlyjs="cdn")