feat(26-01): widen template explorer dialog with two-column card layout

- Increase dialog max-width from 4xl to 6xl
- Increase max-height from 80vh to 85vh
- Change card layout to two-column grid

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/quickstart/TemplateExplorerView.tsx

@@ -399,7 +399,7 @@ export function TemplateExplorerView({
               <h3 className="text-xs font-medium text-neutral-400 uppercase tracking-wider">
                 Quick Start
               </h3>
-              <div className="flex flex-col gap-3">
+              <div className="grid grid-cols-2 gap-3">
                 {filteredPresets.map((preset) => (
                   <TemplateCard
                     key={preset.id}

src/components/quickstart/WelcomeModal.tsx

@@ -79,7 +79,7 @@ export function WelcomeModal({
       className="fixed inset-0 z-[100] flex items-center justify-center bg-black/50 backdrop-blur-sm"
       onWheelCapture={(e) => e.stopPropagation()}
     >
-      <div className="w-full max-w-4xl mx-4 bg-neutral-800 rounded-xl border border-neutral-700 shadow-2xl overflow-clip max-h-[80vh] flex flex-col">
+      <div className="w-full max-w-6xl mx-4 bg-neutral-800 rounded-xl border border-neutral-700 shadow-2xl overflow-clip max-h-[85vh] flex flex-col">
         {currentView === "initial" && (
           <QuickstartInitialView
             onSelectBlankCanvas={handleSelectBlankCanvas}