feat(plotnine): implement bar-sorted (#2563)

## Implementation: `bar-sorted` - plotnine

Implements the **plotnine** version of `bar-sorted`.

**File:** `plots/bar-sorted/implementations/plotnine.py`

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20593350489)*

---------

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

Author: github-actions[bot]

plots/bar-sorted/implementations/plotnine.py

@@ -0,0 +1,53 @@
+""" pyplots.ai
+bar-sorted: Sorted Bar Chart
+Library: plotnine 0.15.2 | Python 3.13.11
+Quality: 92/100 | Created: 2025-12-30
+"""
+
+import pandas as pd
+from plotnine import (
+    aes,
+    element_blank,
+    element_line,
+    element_text,
+    geom_bar,
+    geom_text,
+    ggplot,
+    labs,
+    theme,
+    theme_minimal,
+)
+
+
+# Data - Monthly sales by product category (sorted descending)
+data = {
+    "category": ["Electronics", "Furniture", "Clothing", "Food & Beverage", "Home & Garden", "Sports", "Books", "Toys"],
+    "sales": [4850, 3720, 3150, 2890, 2340, 1980, 1450, 920],
+}
+df = pd.DataFrame(data)
+
+# Sort by sales descending and create ordered categorical for proper bar order
+df = df.sort_values("sales", ascending=False)
+df["category"] = pd.Categorical(df["category"], categories=df["category"], ordered=True)
+
+# Create plot
+plot = (
+    ggplot(df, aes(x="category", y="sales"))
+    + geom_bar(stat="identity", fill="#306998", width=0.7)
+    + geom_text(aes(label="sales"), va="bottom", size=12, nudge_y=80, color="#333333")
+    + labs(x="Product Category", y="Sales ($ thousands)", title="bar-sorted · plotnine · pyplots.ai")
+    + theme_minimal()
+    + theme(
+        figure_size=(16, 9),
+        text=element_text(size=14),
+        axis_title=element_text(size=20),
+        axis_text=element_text(size=16),
+        axis_text_x=element_text(angle=30, ha="right"),
+        plot_title=element_text(size=24),
+        panel_grid_major_x=element_blank(),
+        panel_grid_major_y=element_line(alpha=0.3),
+    )
+)
+
+# Save
+plot.save("plot.png", dpi=300, verbose=False)

plots/bar-sorted/metadata/plotnine.yaml

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+library: plotnine
+specification_id: bar-sorted
+created: '2025-12-30T09:31:01Z'
+updated: '2025-12-30T09:39:05Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20593350489
+issue: 0
+python_version: 3.13.11
+library_version: 0.15.2
+preview_url: https://storage.googleapis.com/pyplots-images/plots/bar-sorted/plotnine/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/bar-sorted/plotnine/plot_thumb.png
+preview_html: null
+quality_score: 92
+review:
+  strengths:
+  - Excellent use of pd.Categorical to enforce sort order in plotnine
+  - Value labels above bars improve readability
+  - Clean ggplot2 grammar of graphics implementation
+  - Good font sizing for high-resolution output
+  - Appropriate rotation of x-axis labels to prevent overlap
+  weaknesses:
+  - Could highlight top category with different color as spec suggests
+  - No random seed comment (data is deterministic but convention not followed)