fix: preserve primary image aspect ratio

.memory/worklog.json

@@ -1573,6 +1573,20 @@
       "message": "fix: improve project brief preview layout",
       "hash": "61e597c",
       "files_changed": 3
+    },
+    {
+      "ts": "2026-05-20T16:48:47+08:00",
+      "type": "commit",
+      "message": "fix: improve project brief preview layout",
+      "hash": "8d4275f",
+      "files_changed": 3
+    },
+    {
+      "ts": "2026-05-20T17:11:41+08:00",
+      "type": "commit",
+      "message": "auto-save 2026-05-20 17:11 (~2)",
+      "hash": "36c93cd",
+      "files_changed": 2
     }
   ]
 }

src/app/page.tsx

@@ -90,6 +90,11 @@ function ProjectBrief({ session }: { session: GenSession }) {
   const generatedAssets = (session.packs ?? []).reduce((sum, pack) => sum + pack.assets.length, 0);
   const totalSlots = packSlotTotal();
   const [previewOpen, setPreviewOpen] = useState(false);
+  const [primaryAspectRatio, setPrimaryAspectRatio] = useState('1 / 1');
+
+  useEffect(() => {
+    setPrimaryAspectRatio('1 / 1');
+  }, [primaryImage?.url]);
 
   return (
     <section className="project-brief-panel">
@@ -114,8 +119,18 @@ function ProjectBrief({ session }: { session: GenSession }) {
           onFocus={() => setPreviewOpen(true)}
           onBlur={() => setPreviewOpen(false)}
         >
-          <div className="project-primary-preview">
-            <img src={primaryImage.url} alt="当前主方案" className="project-primary-image" />
+          <div className="project-primary-preview" style={{ aspectRatio: primaryAspectRatio }}>
+            <img
+              src={primaryImage.url}
+              alt="当前主方案"
+              className="project-primary-image"
+              onLoad={event => {
+                const image = event.currentTarget;
+                if (image.naturalWidth && image.naturalHeight) {
+                  setPrimaryAspectRatio(`${image.naturalWidth} / ${image.naturalHeight}`);
+                }
+              }}
+            />
           </div>
           <div className="project-primary-meta">
             <span className="text-[10px] font-semibold uppercase tracking-[0.16em] text-white/70">Primary</span>