desktop: add brand logo to the top-left corner on Windows/Linux

desktop/src/renderer/assets.d.ts

@@ -0,0 +1,21 @@
+// Type declarations for static asset imports handled by Vite.
+declare module '*.png' {
+  const src: string
+  export default src
+}
+declare module '*.jpg' {
+  const src: string
+  export default src
+}
+declare module '*.jpeg' {
+  const src: string
+  export default src
+}
+declare module '*.svg' {
+  const src: string
+  export default src
+}
+declare module '*.webp' {
+  const src: string
+  export default src
+}

desktop/src/renderer/src/layout/NavRail.tsx

@@ -22,9 +22,12 @@ import {
   Store,
 } from 'lucide-react'
 import type { LucideIcon } from 'lucide-react'
+// The desktop app's own brand icon (transparent PNG), bundled by Vite.
+import brandLogo from '../assets/logo.png'
 import { t, getLang, setLang, Lang } from '../i18n'
 import { useUIStore } from '../store/uiStore'
 import { useTheme } from '../hooks/useTheme'
+import { usePlatform } from '../hooks/usePlatform'
 import { useUpdateStore, hasPendingUpdate } from '../store/updateStore'
 import UpdateBanner from '../components/UpdateBanner'
 
@@ -71,6 +74,10 @@ const NavRail: React.FC<NavRailProps> = ({ onLangChange }) => {
   const navigate = useNavigate()
   const { navCollapsed, toggleNav } = useUIStore()
   const { theme, toggleTheme } = useTheme()
+  // On macOS the top-left is occupied by the native traffic lights, so the
+  // brand mark is only shown on Windows/Linux where that corner is otherwise
+  // empty (mirrors the web console's sidebar logo).
+  const { isMac } = usePlatform()
 
   const collapsed = navCollapsed
   const width = collapsed ? 'w-[56px]' : 'w-[208px]'
@@ -147,8 +154,23 @@ const NavRail: React.FC<NavRailProps> = ({ onLangChange }) => {
   return (
     <aside className={`${width} flex flex-col flex-shrink-0 h-full bg-base transition-[width] duration-200`}>
       {/* Top: full-width drag strip; bottom border continues the header divider
-          across the whole window. No right border so it doesn't cut the lights. */}
+          across the whole window. No right border so it doesn't cut the lights.
-      <div className="titlebar-drag h-[44px] flex-shrink-0 border-b border-default" />
+          On Windows/Linux the top-left corner is empty (no traffic lights), so
+          we surface the brand mark here like the web console's sidebar. */}
+      <div
+        className={`titlebar-drag h-[44px] flex-shrink-0 border-b border-default flex items-center ${
+          collapsed ? 'justify-center px-0' : 'px-3'
+        }`}
+      >
+        {!isMac && (
+          <div className="flex items-center gap-2 min-w-0 select-none">
+            <BrandLogo />
+            {!collapsed && (
+              <span className="text-[14px] font-semibold text-content truncate">CowAgent</span>
+            )}
+          </div>
+        )}
+      </div>
 
       {/* Content area carries the right divider, starting below the titlebar */}
       <div className="flex-1 flex flex-col min-h-0 border-r border-default">
@@ -238,6 +260,18 @@ const NavRail: React.FC<NavRailProps> = ({ onLangChange }) => {
   )
 }
 
+// Brand mark for the top-left corner (Windows/Linux). Uses the desktop app's
+// own icon (transparent PNG with its own rounded shape), so it sits cleanly on
+// both light and dark backgrounds without extra styling.
+const BrandLogo: React.FC = () => (
+  <img
+    src={brandLogo}
+    alt="CowAgent"
+    draggable={false}
+    className="flex-shrink-0 w-7 h-7 object-contain"
+  />
+)
+
 const FooterBtn: React.FC<{
   collapsed: boolean
   onClick: () => void