fix: Prevent agents page from scrolling — lock layout to viewport

Body: height 100vh + overflow hidden instead of min-height 100vh,
so the browser never shows a scrollbar on html/body.
AppLayout: h-screen flex column with shrink-0 header and flex-1
min-h-0 overflow-auto main. Pages like initiatives scroll within
main; agents page uses h-full with internal panel scrollers.

packages/web/src/index.css

@@ -57,7 +57,8 @@
     @apply bg-background text-foreground;
     margin: 0;
     min-width: 320px;
-    min-height: 100vh;
+    height: 100vh;
+    overflow: hidden;
   }
 }
 

packages/web/src/layouts/AppLayout.tsx

@@ -9,9 +9,9 @@ const navItems = [
 
 export function AppLayout({ children }: { children: React.ReactNode }) {
   return (
-    <div className="min-h-screen bg-background">
+    <div className="flex h-screen flex-col bg-background">
       {/* Header */}
-      <header className="sticky top-0 z-50 border-b bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/60">
+      <header className="shrink-0 border-b bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/60">
         <div className="mx-auto flex h-14 max-w-7xl items-center justify-between px-6">
           <Link to="/initiatives" className="text-lg font-bold tracking-tight">
             Codewalk District
@@ -35,7 +35,7 @@ export function AppLayout({ children }: { children: React.ReactNode }) {
       </header>
 
       {/* Page content */}
-      <main className="mx-auto max-w-7xl px-6 py-6">
+      <main className="mx-auto flex-1 min-h-0 w-full max-w-7xl overflow-auto px-6 py-6">
         {children}
       </main>
     </div>

packages/web/src/routes/agents.tsx

@@ -89,10 +89,7 @@ function AgentsPage() {
   // Loading state
   if (agentsQuery.isLoading) {
     return (
-      <div
-        style={{ height: "calc(100vh - 7rem)" }}
-        className="flex flex-col gap-4"
-      >
+      <div className="flex h-full flex-col gap-4">
         <div className="flex items-center justify-between shrink-0">
           <div className="flex items-center gap-2">
             <Skeleton className="h-6 w-20" />
@@ -179,10 +176,7 @@ function AgentsPage() {
   ];
 
   return (
-    <div
-      style={{ height: "calc(100vh - 7rem)" }}
-      className="flex flex-col gap-4"
-    >
+    <div className="flex h-full flex-col gap-4">
       {/* Header + Filters */}
       <div className="shrink-0 space-y-3">
         <div className="flex items-center justify-between">