feat(letsplot): implement area-mountain-panorama (#5408)

## Implementation: `area-mountain-panorama` - python/letsplot

Implements the **python/letsplot** version of `area-mountain-panorama`.

**File:**
`plots/area-mountain-panorama/implementations/python/letsplot.py`

**Parent Issue:** #5365

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/24941216649)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/area-mountain-panorama/implementations/python/letsplot.py

@@ -0,0 +1,157 @@
+""" anyplot.ai
+area-mountain-panorama: Mountain Panorama Profile with Labeled Peaks
+Library: letsplot 4.9.0 | Python 3.14.4
+Quality: 86/100 | Created: 2026-04-25
+"""
+
+import os
+
+import numpy as np
+import pandas as pd
+from lets_plot import (
+    LetsPlot,
+    aes,
+    element_blank,
+    element_line,
+    element_rect,
+    element_text,
+    geom_area,
+    geom_segment,
+    geom_text,
+    ggplot,
+    ggsize,
+    labs,
+    scale_x_continuous,
+    scale_y_continuous,
+    theme,
+    theme_minimal,
+)
+from lets_plot.export import ggsave
+
+
+LetsPlot.setup_html()
+
+# 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"
+INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"
+RULE = "#D6D3C7" if THEME == "light" else "#3A3A34"
+BRAND = "#009E73"
+
+# Data — Wallis (Valais, Switzerland) panorama anchored on the Matterhorn
+peak_records = [
+    ("Matterhorn", 22, 4478),
+    ("Dent Blanche", 46, 4358),
+    ("Ober Gabelhorn", 64, 4063),
+    ("Zinalrothorn", 80, 4221),
+    ("Weisshorn", 96, 4506),
+    ("Dom", 122, 4545),
+    ("Täschhorn", 132, 4491),
+    ("Alphubel", 144, 4206),
+    ("Allalinhorn", 156, 4027),
+    ("Rimpfischhorn", 170, 4199),
+    ("Strahlhorn", 184, 4190),
+    ("Monte Rosa", 212, 4634),
+    ("Liskamm", 230, 4527),
+    ("Castor", 244, 4223),
+    ("Pollux", 252, 4092),
+    ("Breithorn", 268, 4164),
+]
+peaks_df = pd.DataFrame(peak_records, columns=["name", "angle", "elev"])
+
+# Skyline — sum-of-Gaussians around peaks plus minor inter-peak ridges + organic noise
+np.random.seed(42)
+n_samples = 1600
+angle = np.linspace(0, 290, n_samples)
+base_elev = 3000.0
+
+skyline = np.full_like(angle, base_elev)
+for _, p in peaks_df.iterrows():
+    bell = base_elev + (p["elev"] - base_elev) * np.exp(-((angle - p["angle"]) ** 2) / (2 * 7.0**2))
+    skyline = np.maximum(skyline, bell)
+
+minor_offsets = [9, 33, 56, 73, 88, 108, 138, 162, 198, 224, 258, 280]
+for off in minor_offsets:
+    h = 3450 + np.random.uniform(-180, 200)
+    bell = base_elev + (h - base_elev) * np.exp(-((angle - off) ** 2) / (2 * 4.0**2))
+    skyline = np.maximum(skyline, bell)
+
+skyline = skyline + np.cumsum(np.random.randn(n_samples)) * 0.6
+skyline_df = pd.DataFrame({"angle": angle, "elev": skyline})
+
+# Stagger labels into three rows — name labels are wide, so use a generous gap
+label_rows = [5650, 5350, 5050]
+min_dx = 26
+placed = []
+label_y_values = []
+for _, p in peaks_df.iterrows():
+    chosen = label_rows[-1]
+    for ry in label_rows:
+        conflict = any(abs(p["angle"] - pa) < min_dx and pr == ry for pa, pr in placed)
+        if not conflict:
+            chosen = ry
+            break
+    label_y_values.append(chosen)
+    placed.append((p["angle"], chosen))
+peaks_df["label_y"] = label_y_values
+peaks_df["elev_y"] = peaks_df["label_y"] - 140
+peaks_df["elev_text"] = peaks_df["elev"].astype(str) + " m"
+
+# Highlight the anchor summit (Matterhorn) typographically
+anchor_mask = peaks_df["name"] == "Matterhorn"
+anchor_df = peaks_df[anchor_mask]
+other_df = peaks_df[~anchor_mask]
+
+# Compass bearing ticks — vantage point ~Gornergrat sweeping WSW → ENE
+compass_breaks = [22, 90, 160, 230, 280]
+compass_labels = ["WSW", "W", "NW", "N", "NE"]
+
+plot = (
+    ggplot()
+    # Mountain silhouette
+    + geom_area(data=skyline_df, mapping=aes(x="angle", y="elev"), fill=BRAND, color=BRAND, size=0.6, alpha=1.0)
+    # Leader lines from each summit up to its label
+    + geom_segment(
+        data=peaks_df, mapping=aes(x="angle", y="elev", xend="angle", yend="label_y"), color=INK_SOFT, size=0.4
+    )
+    # Peak names — non-anchor
+    + geom_text(
+        data=other_df, mapping=aes(x="angle", y="label_y", label="name"), size=7, color=INK, fontface="bold", vjust=0.0
+    )
+    # Peak names — Matterhorn anchor (slightly larger for visual emphasis)
+    + geom_text(
+        data=anchor_df, mapping=aes(x="angle", y="label_y", label="name"), size=9, color=INK, fontface="bold", vjust=0.0
+    )
+    # Elevation under each name
+    + geom_text(data=peaks_df, mapping=aes(x="angle", y="elev_y", label="elev_text"), size=6, color=INK_SOFT, vjust=0.0)
+    + scale_x_continuous(name="Bearing", breaks=compass_breaks, labels=compass_labels, limits=[0, 290], expand=[0, 0])
+    + scale_y_continuous(name="Elevation (m)", breaks=[3000, 3500, 4000, 4500], limits=[2800, 6000], expand=[0, 0])
+    + labs(
+        title="Wallis Panorama from Gornergrat · area-mountain-panorama · letsplot · anyplot.ai",
+        subtitle="Skyline of the Pennine Alps with 16 labeled 4000-m summits",
+    )
+    + ggsize(1600, 900)
+    + theme_minimal()
+    + theme(
+        plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
+        panel_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
+        panel_grid_major_y=element_line(color=RULE, size=0.3),
+        panel_grid_major_x=element_blank(),
+        panel_grid_minor=element_blank(),
+        axis_line_x=element_line(color=INK_SOFT, size=0.5),
+        axis_line_y=element_blank(),
+        axis_ticks_x=element_line(color=INK_SOFT),
+        axis_ticks_y=element_blank(),
+        axis_title=element_text(size=20, color=INK),
+        axis_text=element_text(size=16, color=INK_SOFT),
+        plot_title=element_text(size=24, color=INK),
+        plot_subtitle=element_text(size=16, color=INK_MUTED),
+        plot_margin=[40, 40, 20, 20],
+    )
+)
+
+ggsave(plot, f"plot-{THEME}.png", path=".", scale=3)
+ggsave(plot, f"plot-{THEME}.html", path=".")