chore(tooling): make the screenshot recipe work with no setup

Two things this session depended on lived only in a scratchpad, so the next
agent would have had to reinvent them from a prose hint:

- scripts/screenshot-fonts.conf, now applied by screenshot.ts itself. Without
  it this container renders every generic font family as Fira Code and the UI
  looks monospaced in a way no user sees — a trap that nearly produced a "fix"
  for a font bug that does not exist.
- scripts/demo-data.ts, which seeds a visibly synthetic dataset. Without it
  every screenshot shows an app full of zeros, because Chrome starts from a
  fresh profile each run.

CLAUDE.md now carries the two-command recipe verbatim instead of "point
FONTCONFIG_FILE at an override", and says why --reload is mandatory. Verified
from a clean shell with no environment set.

Also flags docs/superpowers/plans/2026-09-01-budget-app.md as a historical
record: its snippets still show CURRENCIES and CURRENCY_DIGITS, which no
longer exist, and an agent reading it as current would be misled.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/screenshot.ts

@@ -30,6 +30,19 @@ const width = Number(flag("w", "1280"));
 const height = Number(flag("h", "900"));
 const waitMs = Number(flag("wait", "1500"));
 
+/**
+ * This container's fontconfig resolves EVERY generic family — sans-serif,
+ * system-ui, monospace — to Fira Code, a monospace font. Screenshots then show
+ * the whole UI monospaced in a way no real user sees, and the last agent to
+ * look nearly "fixed" a font bug that did not exist. Applied automatically so
+ * nobody has to know that; set FONTCONFIG_FILE yourself to override.
+ */
+const fontConfig = new URL("./screenshot-fonts.conf", import.meta.url).pathname;
+const fontEnv =
+  process.env.FONTCONFIG_FILE || !(await Bun.file(fontConfig).exists())
+    ? {}
+    : { FONTCONFIG_FILE: fontConfig };
+
 const chrome = Bun.spawn(
   [
     process.env.CHROME ?? "google-chrome",
@@ -49,7 +62,7 @@ const chrome = Bun.spawn(
     ...(has("dark") ? ["--force-dark-mode", "--enable-features=WebContentsForceDark"] : []),
     "about:blank",
   ],
-  { stdout: "ignore", stderr: "pipe" },
+  { stdout: "ignore", stderr: "pipe", env: { ...process.env, ...fontEnv } },
 );
 
 /** Chrome announces its debugging endpoint on stderr, once, at startup. */