feat: 플러그인 설정 섹션 API 도입

docs/content/en/advanced/page.mdx

@@ -171,7 +171,7 @@ dmn.plugin.defineElement({
 
 Only call `setState` when state actually changes:
 
-```javascript
+```javascript fragment=object-members
 onMount: ({ setState, getSettings }) => {
   let lastKps = 0;
 
@@ -185,7 +185,7 @@ onMount: ({ setState, getSettings }) => {
   }, 100);
 
   return () => clearInterval(interval);
-};
+},
 ```
 
 ## Multi-Window Patterns

docs/content/en/api-reference/_meta.js

@@ -6,6 +6,7 @@ export default {
   settings: "Settings",
   overlay: "Overlay",
   "css-js": "CSS/JS",
+  sound: "Sound",
   presets: "Presets",
   i18n: "i18n",
   plugin: "Plugin",

docs/content/en/api-reference/index/page.mdx

@@ -18,6 +18,7 @@ All plugins access DM Note features through the `dmn` global object.
 | [`dmn.knobItems`](/docs/api-reference/knobs)   | HID knob elements                |
 | [`dmn.settings`](/docs/api-reference/settings) | App settings get/set             |
 | [`dmn.overlay`](/docs/api-reference/overlay)   | Overlay control                  |
+| [`dmn.sound`](/docs/api-reference/sound)      | Key sound library                |
 | [`dmn.css`](/docs/api-reference/css-js#css)    | CSS custom code                  |
 | [`dmn.js`](/docs/api-reference/css-js#js)      | JS plugin management             |
 | [`dmn.presets`](/docs/api-reference/presets)   | Preset save/load                 |