Condemn uses, not chart types

The pie page argued the form was the problem ("asks the reader to
compare angles") and then conceded a narrow exception; the dual-axis
page named the form in its title and rated it severity 5. Both read as
blanket bans, which is not the position — and blanket bans are how
dataviz advice turns into the folklore we're trying to replace with
citations.

The pie page now says outright that the chart type isn't the sin, the
workload is, and keeps the pie for the job it does well. The dual-axis
page is retitled for the actual misuse, drops to severity 4, and gains
a section on when a second axis is legitimate — the test being whether
you chose the alignment yourself.

Adds a severity rubric to CLAUDE.md so this stays consistent: 5 is
reserved for charts with no honest reading, and a form with legitimate
uses caps at 4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ULE5RRxdQE1ebwefEd2eCM

CLAUDE.md

@@ -24,6 +24,19 @@ Each sin page follows one shape: **poke → proof → why → the fix → receip
   "Your bars don't start at zero…", not the numbers from our example data.
 - **Tone: cheeky, not moralizing.** "Caught — here are the receipts," not
   "repent." Poke the mistake, keep it light.
+- **We condemn uses, not chart types.** There is no banned form here. A pie
+  chart showing three parts of a whole is doing its job; a second y-axis
+  carrying °C against °F is fine. The sin is always a *use* — the workload the
+  form can't carry, the alignment you picked yourself, the baseline you moved.
+  Say so on the page when the form has honest uses, so nobody reads us as
+  "pie charts are always wrong." Blanket bans are how dataviz advice turns into
+  folklore, and folklore is what we're trying to replace with citations.
+- **Severity means something.** Keep it consistent:
+  **5** — reverses or fabricates meaning; no honest reading of the chart exists.
+  **4** — actively misleads about magnitude or relationship, but the underlying
+  form has legitimate uses. **3** — a sound form asked to do a job it can't; the
+  reader can't extract what the chart claims to show. **2** — craft failure:
+  nothing false, but the reader is made to work for no reason.
 - **Same numbers, both charts.** The bad and fixed charts must share one dataset
   so the page *proves* dishonest-vs-honest by construction. Charts are authored
   as Vega-Lite specs and rendered at build time — never screenshots.