feat(seaborn): implement pie-drilldown (#3120)

## Implementation: `pie-drilldown` - seaborn

Implements the **seaborn** version of `pie-drilldown`.

**File:** `plots/pie-drilldown/implementations/seaborn.py`

**Parent Issue:** #3072

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20620475313)*

---------

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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/pie-drilldown/implementations/seaborn.py

@@ -0,0 +1,140 @@
+""" pyplots.ai
+pie-drilldown: Drilldown Pie Chart with Click Navigation
+Library: seaborn 0.13.2 | Python 3.13.11
+Quality: 82/100 | Created: 2025-12-31
+"""
+
+import matplotlib.pyplot as plt
+import numpy as np
+import seaborn as sns
+
+
+np.random.seed(42)
+
+# Set seaborn style for consistent theming
+sns.set_theme(style="whitegrid", palette="colorblind")
+
+# Data - Sales hierarchy: Region -> Category breakdown
+# Main level (regions)
+main_labels = ["North America", "Europe", "Asia Pacific", "Latin America"]
+main_values = [45000, 32000, 28000, 15000]
+main_total = sum(main_values)
+
+# Drilldown data for "North America" (shown as example of drill-down view)
+drill_labels = ["Electronics", "Clothing", "Home & Garden", "Sports", "Books"]
+drill_values = [18000, 12000, 8000, 4500, 2500]
+drill_total = sum(drill_values)
+
+# Use seaborn color palette
+main_colors = sns.color_palette("colorblind", n_colors=len(main_labels))
+drill_colors = sns.color_palette("Blues_r", n_colors=len(drill_labels))
+
+# Create figure with two subplots showing drilldown concept
+fig, axes = plt.subplots(1, 2, figsize=(16, 9))
+
+# Left chart - Main level pie chart (all regions)
+ax1 = axes[0]
+
+# Explode the first slice to show it's selected for drilldown
+explode_main = [0.08, 0, 0, 0]
+
+_, _, autotexts1 = ax1.pie(
+    main_values,
+    labels=main_labels,
+    colors=main_colors,
+    autopct=lambda pct: f"{pct:.1f}%\n(${int(pct * main_total / 100):,})",
+    explode=explode_main,
+    startangle=140,
+    pctdistance=0.55,
+    labeldistance=1.18,
+    wedgeprops={"edgecolor": "white", "linewidth": 2},
+    textprops={"fontsize": 14},
+)
+
+# Style the percentage labels
+for autotext in autotexts1:
+    autotext.set_fontsize(12)
+    autotext.set_fontweight("bold")
+    autotext.set_color("white")
+
+# Add click indicator annotation pointing to North America
+ax1.annotate(
+    "Click to\ndrill down",
+    xy=(0.25, 0.45),
+    xycoords="axes fraction",
+    fontsize=12,
+    ha="center",
+    fontweight="bold",
+    bbox={"boxstyle": "round,pad=0.4", "facecolor": "#FFD43B", "edgecolor": "#306998", "alpha": 0.9},
+    arrowprops={"arrowstyle": "->", "color": "#306998", "lw": 2, "connectionstyle": "arc3,rad=0.2"},
+    xytext=(0.05, 0.25),
+)
+
+ax1.set_title("All Regions", fontsize=22, fontweight="bold", pad=15)
+
+# Right chart - Drilldown pie chart (North America breakdown)
+ax2 = axes[1]
+
+_, _, autotexts2 = ax2.pie(
+    drill_values,
+    labels=drill_labels,
+    colors=drill_colors,
+    autopct=lambda pct: f"{pct:.1f}%\n(${int(pct * drill_total / 100):,})",
+    startangle=45,
+    pctdistance=0.55,
+    labeldistance=1.20,
+    wedgeprops={"edgecolor": "white", "linewidth": 2},
+    textprops={"fontsize": 14},
+)
+
+# Style the percentage labels
+for autotext in autotexts2:
+    autotext.set_fontsize(11)
+    autotext.set_fontweight("bold")
+    autotext.set_color("white")
+
+ax2.set_title("North America Breakdown", fontsize=22, fontweight="bold", pad=15)
+
+# Add breadcrumb trail above drilldown chart
+ax2.annotate(
+    "All > North America",
+    xy=(0.5, 1.08),
+    xycoords="axes fraction",
+    fontsize=14,
+    ha="center",
+    bbox={"boxstyle": "round,pad=0.4", "facecolor": "#f0f0f0", "edgecolor": "#306998", "alpha": 0.9},
+)
+
+# Add back button indicator
+ax2.annotate(
+    "← Back",
+    xy=(0.05, 1.08),
+    xycoords="axes fraction",
+    fontsize=13,
+    ha="left",
+    color="#306998",
+    fontweight="bold",
+    bbox={"boxstyle": "round,pad=0.3", "facecolor": "white", "edgecolor": "#306998"},
+)
+
+# Add arrow between charts to show drilldown flow
+fig.patches.extend(
+    [plt.Arrow(0.48, 0.5, 0.04, 0, width=0.06, transform=fig.transFigure, facecolor="#306998", edgecolor="white")]
+)
+
+# Main title
+fig.suptitle("pie-drilldown · seaborn · pyplots.ai", fontsize=26, fontweight="bold", y=0.98)
+
+# Subtitle explaining the visualization
+fig.text(
+    0.5,
+    0.02,
+    "Static representation of drilldown: Click any slice to explore subcategories",
+    ha="center",
+    fontsize=14,
+    style="italic",
+    color="#666666",
+)
+
+plt.tight_layout(rect=[0, 0.05, 1, 0.93])
+plt.savefig("plot.png", dpi=300, bbox_inches="tight")

plots/pie-drilldown/metadata/seaborn.yaml

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+library: seaborn
+specification_id: pie-drilldown
+created: '2025-12-31T14:04:27Z'
+updated: '2025-12-31T15:26:51Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20620475313
+issue: 3072
+python_version: 3.13.11
+library_version: 0.13.2
+preview_url: https://storage.googleapis.com/pyplots-images/plots/pie-drilldown/seaborn/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/pie-drilldown/seaborn/plot_thumb.png
+preview_html: null
+quality_score: 82
+review:
+  strengths:
+  - Effectively communicates the drilldown concept with side-by-side pie charts and
+    connecting arrow
+  - Excellent breadcrumb navigation and back button UI elements
+  - Good colorblind-safe palette on main chart, appropriate sequential blues for drilldown
+  - Clean, professional layout with clear visual hierarchy
+  - Percentage and dollar value labels on all slices enhance readability
+  - Click to drill down annotation clearly indicates interactivity concept
+  weaknesses:
+  - Seaborn is used only for theming and color palettes; core visualization uses matplotlib
+    pie() - this is a library limitation since seaborn does not have a native pie
+    chart function
+  - 'Some percentage labels in smaller slices (Books: 5.6%) appear cramped within
+    the slice'
+  - Only demonstrates one drilldown path (North America); spec suggests showing navigation
+    capability more fully