feat(letsplot): implement ecdf-basic (#9491)

## Implementation: `ecdf-basic` - python/letsplot

Implements the **python/letsplot** version of `ecdf-basic`.

**File:** `plots/ecdf-basic/implementations/python/letsplot.py`

**Parent Issue:** #976

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/28161022176)*

---------

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/ecdf-basic/implementations/python/letsplot.py

@@ -1,7 +1,7 @@
 """ anyplot.ai
 ecdf-basic: Basic ECDF Plot
-Library: letsplot 4.9.0 | Python 3.14.4
-Quality: 87/100 | Updated: 2026-04-24
+Library: letsplot 4.10.1 | Python 3.13.14
+Quality: 88/100 | Updated: 2026-06-25
 """
 
 import os
@@ -15,9 +15,13 @@
     element_line,
     element_rect,
     element_text,
+    geom_hline,
+    geom_text,
+    geom_vline,
     ggplot,
     ggsize,
     labs,
+    layer_tooltips,
     scale_y_continuous,
     stat_ecdf,
     theme,
@@ -31,44 +35,74 @@
 # 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"
-GRID = "#C9C7C1" if THEME == "light" else "#565551"
+GRID = "#D8D7D0" if THEME == "light" else "#3A3A36"
 BRAND = "#009E73"
+AMBER = "#DDCC77"
 
-# Data — Web service response times (ms) with mixed distribution
+# Data — web service response times (ms) with bimodal distribution
 np.random.seed(42)
 response_times = np.concatenate(
     [np.random.exponential(scale=50, size=150), np.random.normal(loc=200, scale=30, size=50)]
 )
 df = pd.DataFrame({"response_time": response_times})
 
-# Plot — ECDF using stat_ecdf with step geometry
+# Percentile x-values for storytelling annotations
+p25_x = np.percentile(response_times, 25)
+p50_x = np.percentile(response_times, 50)
+p75_x = np.percentile(response_times, 75)
+pct_df = pd.DataFrame(
+    {
+        "x": [p25_x, p50_x, p75_x],
+        "y": [0.25, 0.5, 0.75],
+        "label": [f"P25: {p25_x:.0f} ms", f"P50: {p50_x:.0f} ms", f"P75: {p75_x:.0f} ms"],
+    }
+)
+# Inflection annotation data (geom_text instead of annotate)
+inflection_df = pd.DataFrame({"x": [45], "y": [0.1], "label": ["Bimodal inflection: ~40 ms"]})
+
+# Title — 3-part format
+title = "ecdf-basic · python · letsplot · anyplot.ai"
+
+# Plot — ECDF with percentile reference lines, bimodal inflection marker, and text annotations
 plot = (
     ggplot(df, aes(x="response_time"))
-    + stat_ecdf(geom="step", color=BRAND, size=2)
-    + labs(
-        x="Response Time (ms)",
-        y="Cumulative Proportion",
-        title="Web Service Response Times · ecdf-basic · letsplot · anyplot.ai",
+    # Background reference lines drawn first so ECDF renders on top
+    + geom_hline(yintercept=0.25, color=INK_SOFT, linetype="dashed", size=0.5, alpha=0.5)
+    + geom_hline(yintercept=0.5, color=INK_SOFT, linetype="dashed", size=0.5, alpha=0.5)
+    + geom_hline(yintercept=0.75, color=INK_SOFT, linetype="dashed", size=0.5, alpha=0.5)
+    # Bimodal inflection marker — gap between exponential fast-path and compute cluster
+    + geom_vline(xintercept=40, color=AMBER, linetype="dotted", size=0.7, alpha=0.7)
+    # Main ECDF step line — drawn on top of reference elements
+    + stat_ecdf(
+        geom="step", color=BRAND, size=1.5, tooltips=layer_tooltips().line("Response Time: @response_time{,.0f} ms")
     )
+    # Percentile x-value labels at each reference line
+    + geom_text(data=pct_df, mapping=aes(x="x", y="y", label="label"), color=INK_SOFT, size=3.5, hjust=0, vjust=-0.5)
+    # Inflection annotation label
+    + geom_text(data=inflection_df, mapping=aes(x="x", y="y", label="label"), color=AMBER, size=3.5, hjust=0)
+    + labs(x="Response Time (ms)", y="Cumulative Proportion", title=title)
     + scale_y_continuous(limits=[0, 1], breaks=[0, 0.25, 0.5, 0.75, 1.0])
-    + ggsize(1600, 900)
+    + ggsize(800, 450)
     + theme_minimal()
     + theme(
         plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
         panel_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
-        legend_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
-        panel_grid_major=element_line(color=GRID, size=0.6),
+        panel_border=element_rect(color=GRID, fill=None, size=0.5),
+        legend_background=element_rect(fill=ELEVATED_BG, color=INK_SOFT),
+        panel_grid_major=element_line(color=GRID, size=0.5),
         panel_grid_minor=element_blank(),
         axis_line=element_line(color=INK_SOFT, size=0.6),
         axis_ticks=element_line(color=INK_SOFT, size=0.5),
-        axis_text=element_text(size=16, color=INK_SOFT),
-        axis_title=element_text(size=20, color=INK),
-        plot_title=element_text(size=24, color=INK),
+        axis_text=element_text(size=10, color=INK_SOFT, family="monospace"),
+        axis_title=element_text(size=12, color=INK),
+        plot_title=element_text(size=16, color=INK),
+        plot_margin=[10, 10, 10, 10],
     )
 )
 
 # Save
-ggsave(plot, filename=f"plot-{THEME}.png", path=".", scale=3)
+ggsave(plot, filename=f"plot-{THEME}.png", path=".", scale=4)
 ggsave(plot, filename=f"plot-{THEME}.html", path=".")