feat(plotnine): implement bullet-basic (#1037)

## Implementation: `bullet-basic` - plotnine

Implements the **plotnine** version of `bullet-basic`.

**File:** `plots/bullet-basic/implementations/plotnine.py`

**Parent Issue:** #999

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20257947684)*

---------

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/bullet-basic/implementations/plotnine.py

@@ -0,0 +1,116 @@
+"""
+bullet-basic: Basic Bullet Chart
+Library: plotnine
+"""
+
+import pandas as pd
+from plotnine import (
+    aes,
+    coord_flip,
+    element_blank,
+    element_text,
+    geom_rect,
+    geom_segment,
+    ggplot,
+    labs,
+    scale_fill_manual,
+    scale_y_continuous,
+    theme,
+    theme_minimal,
+)
+
+
+# Data - Multiple KPIs with different performance levels
+metrics = [
+    {"label": "Revenue", "actual": 275, "target": 250, "ranges": [150, 225, 300]},
+    {"label": "Profit", "actual": 22, "target": 26, "ranges": [15, 22.5, 30]},
+    {"label": "Orders", "actual": 1050, "target": 1100, "ranges": [600, 900, 1200]},
+    {"label": "Satisfaction", "actual": 4.5, "target": 4.2, "ranges": [2.5, 3.5, 5.0]},
+]
+
+# Build data for the plot - normalize all values to 0-100 scale for consistent display
+range_data = []
+actual_data = []
+target_data = []
+label_data = []
+
+for i, m in enumerate(metrics):
+    y_pos = i
+    max_val = m["ranges"][-1]
+
+    # Qualitative ranges (poor, satisfactory, good)
+    range_data.append({"y": y_pos, "xmin": 0, "xmax": (m["ranges"][0] / max_val) * 100, "band": "Poor"})
+    range_data.append(
+        {
+            "y": y_pos,
+            "xmin": (m["ranges"][0] / max_val) * 100,
+            "xmax": (m["ranges"][1] / max_val) * 100,
+            "band": "Satisfactory",
+        }
+    )
+    range_data.append({"y": y_pos, "xmin": (m["ranges"][1] / max_val) * 100, "xmax": 100, "band": "Good"})
+
+    # Actual value bar
+    actual_pct = (m["actual"] / max_val) * 100
+    actual_data.append({"y": y_pos, "xmin": 0, "xmax": actual_pct})
+
+    # Target marker
+    target_pct = (m["target"] / max_val) * 100
+    target_data.append({"y": y_pos, "target": target_pct})
+
+    # Labels with actual values
+    label_data.append({"y": y_pos, "label": m["label"], "actual": m["actual"]})
+
+df_ranges = pd.DataFrame(range_data)
+df_actual = pd.DataFrame(actual_data)
+df_target = pd.DataFrame(target_data)
+df_labels = pd.DataFrame(label_data)
+
+# Grayscale colors for qualitative bands (poor=dark, satisfactory=medium, good=light)
+band_colors = {"Poor": "#D0D0D0", "Satisfactory": "#A0A0A0", "Good": "#707070"}
+
+# Bar height parameters
+range_height = 0.7
+actual_height = 0.3
+
+# Plot
+plot = (
+    ggplot()
+    # Background qualitative ranges
+    + geom_rect(
+        df_ranges, aes(xmin="xmin", xmax="xmax", ymin="y - range_height/2", ymax="y + range_height/2", fill="band")
+    )
+    + scale_fill_manual(values=band_colors, limits=["Good", "Satisfactory", "Poor"], guide=None)
+    # Actual value bar (Python Blue)
+    + geom_rect(
+        df_actual, aes(xmin="xmin", xmax="xmax", ymin="y - actual_height/2", ymax="y + actual_height/2"), fill="#306998"
+    )
+    # Target marker (thin black line)
+    + geom_segment(
+        df_target,
+        aes(x="target", xend="target", y="y - range_height/2.5", yend="y + range_height/2.5"),
+        color="black",
+        size=2.5,
+    )
+    # Flip coordinates for horizontal bullet charts
+    + coord_flip()
+    # Scale and labels
+    + scale_y_continuous(breaks=list(range(len(metrics))), labels=[m["label"] for m in metrics], expand=(0.1, 0.1))
+    + labs(title="bullet-basic · plotnine · pyplots.ai", x="", y="Performance (%)")
+    # Theme
+    + theme_minimal()
+    + theme(
+        figure_size=(16, 9),
+        plot_title=element_text(size=24, ha="center"),
+        axis_title_x=element_text(size=20),
+        axis_title_y=element_blank(),
+        axis_text_x=element_text(size=16),
+        axis_text_y=element_text(size=18),
+        panel_grid_major_y=element_blank(),
+        panel_grid_minor=element_blank(),
+        legend_position="none",
+    )
+)
+
+# Save
+plot.save("plot.png", dpi=300, verbose=False)

plots/bullet-basic/metadata/plotnine.yaml

@@ -0,0 +1,23 @@
+# Per-library metadata for plotnine implementation of bullet-basic
+# Auto-generated by impl-generate.yml
+
+library: plotnine
+specification_id: bullet-basic
+
+# Preview URLs (filled by workflow)
+preview_url: https://storage.googleapis.com/pyplots-images/plots/bullet-basic/plotnine/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/bullet-basic/plotnine/plot_thumb.png
+preview_html: null
+
+current:
+  version: 0
+  generated_at: 2025-12-16T05:51:53Z
+  generated_by: claude-opus-4-5-20251101
+  workflow_run: 20257947684
+  issue: 999
+  quality_score: 93
+  # Version info (filled by workflow)
+  python_version: "3.13.11"
+  library_version: "unknown"
+
+history: []