feat(HAI-001): move new task creation to triage column with button in column header

packages/dashboard/app/components/Header.tsx

@@ -1,17 +1,10 @@
-interface HeaderProps {
-  onNewTask: () => void;
-}
-
-export function Header({ onNewTask }: HeaderProps) {
+export function Header() {
   return (
     <header className="header">
       <div className="header-left">
         <h1 className="logo">hai</h1>
         <span className="logo-sub">board</span>
       </div>
-      <button className="btn btn-primary" onClick={onNewTask}>
-        + New Task
-      </button>
     </header>
   );
 }