feat(web): Linear-inspired sidebar with floating panel layout

- Add canvas background color for the base layer
- Sidebar blends into canvas, no border separator
- Content area rendered as floating white panel with rounded corners
  and shadow, offset from edges to reveal canvas underneath
- Simplify sidebar nav to: Inbox, Agents, Issues, Knowledge Base
- Add workspace switcher header with MulticaIcon

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/app/(dashboard)/layout.tsx

@@ -6,16 +6,16 @@ import {
   Inbox,
   ListTodo,
   Bot,
-  Columns3,
-  Settings,
+  BookOpen,
+  ChevronDown,
 } from "lucide-react";
+import { MulticaIcon } from "@multica/ui/components/multica-icon";
 
 const navItems = [
   { href: "/inbox", label: "Inbox", icon: Inbox },
-  { href: "/issues", label: "Issues", icon: ListTodo },
-  { href: "/board", label: "Board", icon: Columns3 },
   { href: "/agents", label: "Agents", icon: Bot },
-  { href: "/settings", label: "Settings", icon: Settings },
+  { href: "/issues", label: "Issues", icon: ListTodo },
+  { href: "/knowledge-base", label: "Knowledge Base", icon: BookOpen },
 ];
 
 export default function DashboardLayout({
@@ -26,26 +26,34 @@ export default function DashboardLayout({
   const pathname = usePathname();
 
   return (
-    <div className="flex h-screen">
-      {/* Sidebar */}
-      <aside className="flex w-56 flex-col border-r bg-card">
-        <div className="flex h-14 items-center gap-2 border-b px-4">
-          <span className="text-lg font-bold">Multica</span>
+    <div className="flex h-screen bg-canvas">
+      {/* Sidebar — sits on the canvas layer */}
+      <aside className="flex w-56 shrink-0 flex-col">
+        {/* Workspace Switcher */}
+        <div className="flex h-12 items-center gap-2 px-3">
+          <MulticaIcon className="size-4" noSpin />
+          <span className="flex-1 truncate text-sm font-semibold">
+            Multica
+          </span>
+          <ChevronDown className="h-3.5 w-3.5 text-muted-foreground" />
         </div>
-        <nav className="flex-1 space-y-1 p-2">
+
+        {/* Navigation */}
+        <nav className="flex-1 space-y-0.5 px-2">
           {navItems.map((item) => {
-            const isActive = pathname.startsWith(item.href);
+            const isActive =
+              pathname === item.href || pathname.startsWith(item.href + "/");
             return (
               <Link
                 key={item.href}
                 href={item.href}
-                className={`flex items-center gap-3 rounded-md px-3 py-2 text-sm transition-colors ${
+                className={`flex items-center gap-2.5 rounded-md px-2.5 py-1.5 text-sm transition-colors ${
                   isActive
-                    ? "bg-accent text-accent-foreground"
-                    : "text-muted-foreground hover:bg-accent/50"
+                    ? "bg-sidebar-accent text-sidebar-accent-foreground font-medium"
+                    : "text-sidebar-foreground/60 hover:bg-sidebar-accent/50 hover:text-sidebar-foreground"
                 }`}
               >
-                <item.icon className="h-4 w-4" />
+                <item.icon className="h-4 w-4 shrink-0" />
                 {item.label}
               </Link>
             );
@@ -53,8 +61,12 @@ export default function DashboardLayout({
         </nav>
       </aside>
 
-      {/* Main content */}
-      <main className="flex-1 overflow-auto">{children}</main>
+      {/* Main content — floating panel on top of the canvas */}
+      <div className="flex-1 pt-1.5 pr-1.5 pb-1.5">
+        <main className="h-full overflow-auto rounded-xl bg-background shadow-sm">
+          {children}
+        </main>
+      </div>
     </div>
   );
 }

packages/ui/src/styles/globals.css

@@ -86,6 +86,7 @@
   --font-sans: var(--font-sans);
   --font-mono: var(--font-geist-mono);
   --font-brand: var(--font-brand);
+  --color-canvas: var(--canvas);
   --color-sidebar-ring: var(--sidebar-ring);
   --color-sidebar-border: var(--sidebar-border);
   --color-sidebar-accent-foreground: var(--sidebar-accent-foreground);
@@ -156,7 +157,8 @@
   --chart-4: oklch(0.828 0.189 84.429);
   --chart-5: oklch(0.769 0.188 70.08);
   --radius: 0.625rem;
-  --sidebar: oklch(0.985 0 0);
+  --canvas: oklch(0.95 0.002 286);
+  --sidebar: oklch(0.95 0.002 286);
   --sidebar-foreground: oklch(0.141 0.005 285.823);
   --sidebar-primary: oklch(0.205 0.006 285.885);
   --sidebar-primary-foreground: oklch(0.985 0 0);
@@ -204,7 +206,8 @@
   --chart-3: oklch(0.769 0.188 70.08);
   --chart-4: oklch(0.627 0.265 303.9);
   --chart-5: oklch(0.645 0.246 16.439);
-  --sidebar: oklch(0.21 0.006 285.885);
+  --canvas: oklch(0.2 0.005 286);
+  --sidebar: oklch(0.2 0.005 286);
   --sidebar-foreground: oklch(0.985 0 0);
   --sidebar-primary: oklch(0.922 0.006 285.885);
   --sidebar-primary-foreground: oklch(0.205 0.006 285.885);