feat(bokeh): implement dumbbell-basic (#9565)

## Implementation: `dumbbell-basic` - python/bokeh

Implements the **python/bokeh** version of `dumbbell-basic`.

**File:** `plots/dumbbell-basic/implementations/python/bokeh.py`

**Parent Issue:** #945

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/28480554709)*

---------

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/dumbbell-basic/implementations/python/bokeh.py

@@ -1,14 +1,25 @@
 """ anyplot.ai
 dumbbell-basic: Basic Dumbbell Chart
-Library: bokeh 3.9.0 | Python 3.14.4
-Quality: 88/100 | Updated: 2026-04-26
+Library: bokeh 3.9.1 | Python 3.13.14
+Quality: 88/100 | Updated: 2026-06-30
 """
 
 import os
+import sys
+import time
+from pathlib import Path
 
-from bokeh.io import export_png, output_file, save
-from bokeh.models import ColumnDataSource, HoverTool
+
+# Remove script's own directory from sys.path to prevent self-shadowing
+# (this file is named bokeh.py; without this, `import bokeh` would find itself)
+_here = os.path.dirname(os.path.abspath(__file__))
+sys.path = [p for p in sys.path if os.path.abspath(p or ".") != _here]
+
+from bokeh.io import output_file, save
+from bokeh.models import ColumnDataSource, HoverTool, LabelSet
 from bokeh.plotting import figure
+from selenium import webdriver
+from selenium.webdriver.chrome.options import Options
 
 
 # Theme tokens
@@ -17,11 +28,10 @@
 ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
 INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
 INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
-BRAND = "#009E73"  # Okabe-Ito 1 — "Before"
-ACCENT = "#C475FD"  # Okabe-Ito 2 — "After"
+BRAND = "#009E73"  # Imprint palette position 1 — "Before" dots
+ACCENT = "#C475FD"  # Imprint palette position 2 — "After" dots
 
 # Data — Employee satisfaction scores before and after policy changes
-# (one department regressed, the rest improved by varying amounts)
 categories = [
     "Engineering",
     "Marketing",
@@ -44,83 +54,133 @@
 deltas = [d[3] for d in ordered]
 
 # Plot
+TITLE = "dumbbell-basic · python · bokeh · anyplot.ai"
 p = figure(
-    width=4800,
-    height=2700,
+    width=3200,
+    height=1800,
     y_range=categories,
     x_range=(45, 95),
-    title="Employee Satisfaction · dumbbell-basic · bokeh · anyplot.ai",
+    title=TITLE,
     x_axis_label="Satisfaction Score",
     y_axis_label="Department",
     background_fill_color=PAGE_BG,
     border_fill_color=PAGE_BG,
     toolbar_location=None,
+    min_border_bottom=160,
+    min_border_left=280,
+    min_border_top=110,
+    min_border_right=60,
 )
 
-# Connecting segments — thin, subtle, behind the dots
+# Connecting segments — color-coded by direction: green = improvement, red = regression
 seg_source = ColumnDataSource(
-    data={"y": categories, "x_start": start_values, "x_end": end_values, "delta": [f"{d:+d}" for d in deltas]}
+    data={
+        "y": categories,
+        "x_start": start_values,
+        "x_end": end_values,
+        "delta": [f"{d:+d}" for d in deltas],
+        "seg_color": [BRAND if d > 0 else "#AE3030" for d in deltas],
+    }
 )
 p.segment(
-    x0="x_start", x1="x_end", y0="y", y1="y", source=seg_source, line_color=INK_SOFT, line_alpha=0.45, line_width=4
+    x0="x_start", x1="x_end", y0="y", y1="y", source=seg_source, line_color="seg_color", line_alpha=0.55, line_width=6
+)
+
+# Delta labels on connecting segments — makes improvement/regression story explicit
+label_source = ColumnDataSource(
+    data={
+        "x": [(s + e) / 2 for s, e in zip(start_values, end_values, strict=True)],
+        "y": categories,
+        "text": [f"{d:+d}" for d in deltas],
+    }
+)
+p.add_layout(
+    LabelSet(
+        x="x",
+        y="y",
+        text="text",
+        source=label_source,
+        text_align="center",
+        text_baseline="bottom",
+        text_font_size="26pt",
+        text_color=INK_SOFT,
+        y_offset=24,
+    )
 )
 
-# "Before" dots — Okabe-Ito brand green
-before_source = ColumnDataSource(data={"x": start_values, "y": categories, "phase": ["Before"] * len(categories)})
+# "Before" dots — Imprint palette position 1 (brand green)
+before_source = ColumnDataSource(
+    data={
+        "x": start_values,
+        "y": categories,
+        "phase": ["Before"] * len(categories),
+        "after": end_values,
+        "delta": [f"{d:+d} pts" for d in deltas],
+    }
+)
 before_glyph = p.scatter(
     x="x",
     y="y",
     source=before_source,
-    size=34,
+    size=28,
     fill_color=BRAND,
     line_color=PAGE_BG,
-    line_width=2,
+    line_width=3,
     legend_label="Before policy changes",
 )
 
-# "After" dots — Okabe-Ito vermillion
-after_source = ColumnDataSource(data={"x": end_values, "y": categories, "phase": ["After"] * len(categories)})
+# "After" dots — Imprint palette position 2 (lavender)
+after_source = ColumnDataSource(
+    data={
+        "x": end_values,
+        "y": categories,
+        "phase": ["After"] * len(categories),
+        "before": start_values,
+        "delta": [f"{d:+d} pts" for d in deltas],
+    }
+)
 after_glyph = p.scatter(
     x="x",
     y="y",
     source=after_source,
-    size=34,
+    size=28,
     fill_color=ACCENT,
     line_color=PAGE_BG,
-    line_width=2,
+    line_width=3,
     legend_label="After policy changes",
 )
 
-# Hover tooltip (HTML interactivity)
+# Hover tooltip — shows department, phase, score, and delta change together
 p.add_tools(
     HoverTool(
-        renderers=[before_glyph, after_glyph], tooltips=[("Department", "@y"), ("Phase", "@phase"), ("Score", "@x")]
+        renderers=[before_glyph, after_glyph],
+        tooltips=[("Department", "@y"), ("Phase", "@phase"), ("Score", "@x"), ("Δ Change", "@delta")],
     )
 )
 
-# Typography
-p.title.text_font_size = "36pt"
+# Typography — canonical sizes for 3200×1800 per bokeh.md
+p.title.text_font_size = "50pt"
 p.title.text_color = INK
 p.title.text_font_style = "normal"
 p.title.align = "center"
 
-p.xaxis.axis_label_text_font_size = "24pt"
-p.yaxis.axis_label_text_font_size = "24pt"
-p.xaxis.major_label_text_font_size = "20pt"
-p.yaxis.major_label_text_font_size = "20pt"
+p.xaxis.axis_label_text_font_size = "42pt"
+p.yaxis.axis_label_text_font_size = "36pt"
+p.xaxis.major_label_text_font_size = "34pt"
+p.yaxis.major_label_text_font_size = "34pt"
 p.xaxis.axis_label_text_color = INK
 p.yaxis.axis_label_text_color = INK
 p.xaxis.major_label_text_color = INK_SOFT
 p.yaxis.major_label_text_color = INK_SOFT
 p.xaxis.axis_label_standoff = 18
 p.yaxis.axis_label_standoff = 18
 
-# Spines and ticks — keep an L-shape, suppress chart outline
+# Spines — keep x-axis, remove y-axis for a cleaner look
 p.outline_line_color = None
 p.xaxis.axis_line_color = INK_SOFT
-p.yaxis.axis_line_color = INK_SOFT
+p.yaxis.axis_line_color = None
 p.xaxis.major_tick_line_color = INK_SOFT
-p.yaxis.major_tick_line_color = INK_SOFT
+p.yaxis.major_tick_line_color = None
 p.xaxis.minor_tick_line_color = None
 p.yaxis.minor_tick_line_color = None
 
@@ -129,19 +189,46 @@
 p.xgrid.grid_line_alpha = 0.10
 p.ygrid.grid_line_color = None
 
-# Legend — placed inside top-left so it never collides with the data range
-p.legend.location = "top_left"
+# Legend
+p.legend.location = "bottom_left"
 p.legend.background_fill_color = ELEVATED_BG
 p.legend.background_fill_alpha = 0.95
 p.legend.border_line_color = INK_SOFT
 p.legend.border_line_alpha = 0.4
 p.legend.label_text_color = INK_SOFT
-p.legend.label_text_font_size = "20pt"
+p.legend.label_text_font_size = "34pt"
 p.legend.spacing = 10
 p.legend.padding = 18
 p.legend.margin = 24
 
-# Save
-export_png(p, filename=f"plot-{THEME}.png")
-output_file(f"plot-{THEME}.html", title="Employee Satisfaction · dumbbell-basic · bokeh · anyplot.ai")
+# Save interactive HTML (required catalog artifact)
+html_path = Path(f"plot-{THEME}.html")
+output_file(str(html_path), title=TITLE)
 save(p)
+
+# Inject body background CSS to prevent thin border artifact in headless-Chrome screenshot
+html_content = html_path.read_text()
+body_style = f"<style>body{{margin:0;padding:0;background:{PAGE_BG};}}</style>"
+html_content = html_content.replace("</head>", f"{body_style}\n</head>", 1)
+html_path.write_text(html_content)
+
+# Screenshot via headless Chrome — use CDP to set exact viewport to match figure dimensions
+W, H = 3200, 1800
+opts = Options()
+for arg in (
+    "--headless=new",
+    "--no-sandbox",
+    "--disable-dev-shm-usage",
+    "--disable-gpu",
+    f"--window-size={W},{H}",
+    "--hide-scrollbars",
+):
+    opts.add_argument(arg)
+driver = webdriver.Chrome(options=opts)
+driver.execute_cdp_cmd(
+    "Emulation.setDeviceMetricsOverride", {"width": W, "height": H, "deviceScaleFactor": 1, "mobile": False}
+)
+driver.get(f"file://{html_path.resolve()}")
+time.sleep(3)
+driver.save_screenshot(f"plot-{THEME}.png")
+driver.quit()