feat: make app workspaces resizable

apps/dataset-builder/index.html

@@ -36,8 +36,8 @@
         </div>
       </header>
 
-      <main class="builder-layout">
-        <section class="scene-workspace" aria-label="장면 편집 화면">
+      <main class="builder-layout" id="builder-layout" data-split-layout>
+        <section class="scene-workspace" id="builder-workspace" aria-label="장면 편집 화면">
           <div class="workspace-heading">
             <div>
               <p class="eyebrow">01 · 입력과 배치</p>
@@ -97,7 +97,20 @@
           </section>
         </section>
 
-        <aside class="control-panel" aria-label="장면 파라미터">
+        <div
+          class="split-handle"
+          id="builder-split-handle"
+          role="separator"
+          tabindex="0"
+          aria-label="장면 설정 패널 너비 조절"
+          aria-controls="builder-controls"
+          aria-orientation="vertical"
+          data-split-resizer
+          data-storage-key="micarrsim.builder.control-panel-width"
+          title="드래그하거나 방향키로 너비 조절 · Enter/더블클릭으로 초기화"
+        ></div>
+
+        <aside class="control-panel" id="builder-controls" data-split-panel aria-label="장면 파라미터">
           <div class="runtime-line">
             <span class="status-chip status-chip--neutral" data-runtime-status>런타임 확인 중…</span>
             <span class="save-state" id="save-state">기본 장면</span>