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/dual-axis-deception.md

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+---
+title: "The Dual-Axis Deception"
+summary: "Two unrelated series on two independent axes, engineered to look correlated."
+category: "False Relationships"
+severity: 5
+tags: ["dual axis", "correlation", "line chart"]
+badChart: "dual-axis-bad"
+fixedChart: "dual-axis-fixed"
+date: 2026-08-05
+---
+
+## The sin
+
+Put two series on the same plot with two independent y-axes and you can make
+*anything* look correlated. Slide the scales until the lines overlap and the
+reader's brain does the rest: "these move together, so one must cause the other."
+
+## Why it deceives
+
+With independent axes, the vertical position of each line is arbitrary — you
+chose it. Overlapping lines imply a relationship that exists only because you
+tuned two scales to coincide. Ice cream sales and shark attacks both rise in
+summer; neither causes the other. The shared season is the hidden variable.
+
+## The repentance
+
+Don't force two series into one coordinate space just to imply a link. Show them
+in **separate, stacked panels** with honest zero-based scales. If you truly want
+to argue they move together, plot one **against** the other (a scatter plot) and
+let the reader judge the relationship — don't manufacture it with axis scaling.

src/content/sins/pie-chart-overload.md

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+---
+title: "Pie Chart Overload"
+summary: "Eight near-identical slices no human eye can rank. A bar chart was right there."
+category: "Chart-Type Abuse"
+severity: 3
+tags: ["pie chart", "part-to-whole", "comparison"]
+badChart: "pie-overload-bad"
+fixedChart: "pie-overload-fixed"
+date: 2026-08-05
+---
+
+## The sin
+
+The pie chart asks the reader to compare **angles** — something people are
+genuinely bad at. One or two slices, fine. But eight slices, several of them
+within a percentage point of each other? Nobody can tell whether Firefox beats
+Samsung by eyeballing two thin wedges on opposite sides of the circle.
+
+## Why it deceives
+
+Angle and area are hard to judge precisely, and slices scattered around the
+circle can't be lined up against a common baseline. The small categories blur
+into an indistinguishable fringe, and the ranking — usually the whole point —
+becomes guesswork.
+
+## The repentance
+
+Use a **sorted horizontal bar chart**. Every value shares one baseline, the
+ordering is explicit, and long labels sit comfortably beside their bars. Reserve
+the pie for the rare case of two or three parts of an obvious whole — and even
+then, a bar chart rarely does worse.

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

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+---
+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.