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/charts/dual-axis-fixed.json

@@ -0,0 +1,35 @@
+{
+  "title": "Two Series, Shown Separately",
+  "data": {
+    "values": [
+      { "month": "Jan", "icecream": 20, "sharks": 1 },
+      { "month": "Feb", "icecream": 24, "sharks": 1 },
+      { "month": "Mar", "icecream": 38, "sharks": 2 },
+      { "month": "Apr", "icecream": 55, "sharks": 3 },
+      { "month": "May", "icecream": 78, "sharks": 5 },
+      { "month": "Jun", "icecream": 95, "sharks": 6 },
+      { "month": "Jul", "icecream": 100, "sharks": 7 },
+      { "month": "Aug", "icecream": 96, "sharks": 6 }
+    ]
+  },
+  "vconcat": [
+    {
+      "width": 360,
+      "height": 110,
+      "mark": { "type": "line", "color": "#c0392b", "point": true },
+      "encoding": {
+        "x": { "field": "month", "type": "ordinal", "sort": null, "axis": { "title": null, "labels": false } },
+        "y": { "field": "icecream", "type": "quantitative", "scale": { "zero": true }, "title": "Ice cream" }
+      }
+    },
+    {
+      "width": 360,
+      "height": 110,
+      "mark": { "type": "line", "color": "#2980b9", "point": true },
+      "encoding": {
+        "x": { "field": "month", "type": "ordinal", "sort": null, "axis": { "title": null, "labelAngle": 0 } },
+        "y": { "field": "sharks", "type": "quantitative", "scale": { "zero": true }, "title": "Shark attacks" }
+      }
+    }
+  ]
+}