fix(equalizer): redraw curve when <details> reopens (#747)

* fix(equalizer): redraw curve when surrounding <details> toggles open

ResizeObserver does not reliably fire for the `display:none → block`
transition that the SettingsSubSection `<details>` causes when the user
expands the Equalizer panel after collapsing it. drawCurve bails on a
zero-sized canvas (existing macOS-WebKit guard), and without a new
trigger the second open leaves the frequency-response canvas blank.
Add a `toggle` listener on the closest `<details>` ancestor; on open,
redraw after one rAF so the canvas has its laid-out size. Additive —
doesn't change the working ResizeObserver path.

* docs(changelog): note Equalizer canvas redraw fix (#747)

src/components/Equalizer.tsx

@@ -41,6 +41,20 @@ export default function Equalizer() {
     return () => ro.disconnect();
   }, [redraw]);
 
+  // ResizeObserver does not always fire for the `display: none → block`
+  // transition the surrounding <details> causes when toggled, leaving the
+  // canvas blank on the second open. Redraw explicitly when the parent
+  // <details> opens; rAF waits one frame for the canvas to take its size.
+  useEffect(() => {
+    const details = canvasRef.current?.closest('details');
+    if (!details) return;
+    const onToggle = () => {
+      if (details.open) requestAnimationFrame(redraw);
+    };
+    details.addEventListener('toggle', onToggle);
+    return () => details.removeEventListener('toggle', onToggle);
+  }, [redraw]);
+
   const isCustomSaved = activePreset && !BUILTIN_PRESETS.some(p => p.name === activePreset);
   const selectValue = activePreset ?? '__custom__';