fix(ui): replace hardcoded height calc with flex-1 to eliminate bottom blank area

All content panels used h-[calc(100vh-8rem)] which didn't match the
actual available space (CONTENT_TOP_OFFSET is 92px on Mac, 64px on
Win/Linux, not 128px), causing a visible gap at the bottom.

Replace with flex-1 min-h-0 to let panels fill the remaining space
after <main> and any sibling elements (e.g. OpenClaw health banner).

src/components/skills/SkillsPage.tsx

@@ -233,7 +233,7 @@ export const SkillsPage = forwardRef<SkillsPageHandle, SkillsPageProps>(
     }, [skills, searchQuery, filterRepo, filterStatus]);
 
     return (
-      <div className="px-6 flex flex-col h-[calc(100vh-8rem)] overflow-hidden bg-background/50">
+      <div className="px-6 flex flex-col flex-1 min-h-0 overflow-hidden bg-background/50">
         {/* 技能网格（可滚动详情区域） */}
         <div className="flex-1 overflow-y-auto overflow-x-hidden animate-fade-in">
           <div className="py-4">

src/components/skills/UnifiedSkillsPanel.tsx

@@ -250,7 +250,7 @@ const UnifiedSkillsPanel = React.forwardRef<
   }));
 
   return (
-    <div className="px-6 flex flex-col h-[calc(100vh-8rem)] overflow-hidden">
+    <div className="px-6 flex flex-col flex-1 min-h-0 overflow-hidden">
       <AppCountBar
         totalLabel={t("skills.installed", { count: skills?.length || 0 })}
         counts={enabledCounts}