Scaffold Chart Sins site with Astro + build-time Vega-Lite

Set up the static-site tech stack: Astro 5 with Markdown content
collections, Vega-Lite specs rendered to static SVG at build time
(zero client JS), plain scoped CSS, and a GitHub Pages deploy workflow.

Includes three sample sins (truncated y-axis, dual-axis deception,
pie chart overload), each with a bad and fixed chart spec, plus a
gallery index and per-sin detail pages.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XPEvmMbac2fCvKXpQcovj8

src/content/sins/truncated-y-axis.md

@@ -0,0 +1,30 @@
+---
+title: "The Truncated Y-Axis"
+summary: "Chopping the baseline off a bar chart to make small differences look enormous."
+category: "Misleading Scales"
+severity: 4
+tags: ["bar chart", "axis", "exaggeration"]
+badChart: "truncated-axis-bad"
+fixedChart: "truncated-axis-fixed"
+date: 2026-08-05
+---
+
+## The sin
+
+Bar charts encode value with **length**. When you start the y-axis somewhere
+above zero, the bars no longer represent their true magnitudes — a jump from 92
+to 98 (a ~6% change) can be drawn to look like a chart-topping surge. The reader
+compares bar heights and walks away with a wildly inflated sense of the trend.
+
+## Why it deceives
+
+The eye reads the ratio of bar lengths, not the axis labels. Truncating the
+baseline breaks the contract between "twice as tall" and "twice as much." It is
+the single most common way an honest-looking bar chart tells a lie.
+
+## The repentance
+
+Start bar charts at zero. Always. If the interesting variation is genuinely
+small and a zero baseline flattens it, that is a signal to switch encodings —
+use a **line chart** or a **dot plot**, where position (not length) carries the
+meaning and a non-zero range is legitimate.