feat(FN-733): remove redundant Manage Agents button from header

- Remove Manage Agents button from Header component (accessible via sidebar)
- Remove associated onClick handler and prop threading from App.tsx
- Remove Header test cases for the deleted button
- Remove unused useTerminal hook and its tests

packages/dashboard/app/App.tsx

@@ -412,7 +412,6 @@ function AppInner() {
   const handleCloseGitManager = useCallback(() => setGitManagerOpen(false), []);
 
   // Agent handlers
-  const handleOpenAgents = useCallback(() => setAgentsOpen(true), []);
   const handleCloseAgents = useCallback(() => setAgentsOpen(false), []);
 
   // Scripts handlers
@@ -508,7 +507,6 @@ function AppInner() {
         onOpenGitManager={handleOpenGitManager}
         onOpenWorkflowSteps={() => setWorkflowStepsOpen(true)}
         onOpenMissions={viewMode === "project" && currentProject ? () => setMissionsOpen(true) : undefined}
-        onOpenAgents={viewMode === "project" && currentProject ? handleOpenAgents : undefined}
         onOpenScripts={handleOpenScripts}
         onRunScript={handleRunScript}
         onToggleTerminal={handleToggleTerminal}

packages/dashboard/app/components/Header.tsx

@@ -29,7 +29,6 @@ export interface HeaderProps {
   onOpenGitManager?: () => void;
   onOpenWorkflowSteps?: () => void;
   onOpenMissions?: () => void;
-  onOpenAgents?: () => void;
   onOpenScripts?: () => void;
   onRunScript?: (name: string, command: string) => void;
   onToggleTerminal?: () => void;
@@ -79,7 +78,6 @@ export function Header({
   onOpenGitManager,
   onOpenWorkflowSteps,
   onOpenMissions,
-  onOpenAgents,
   onOpenScripts,
   onRunScript,
   onToggleTerminal,
@@ -401,18 +399,6 @@ export function Header({
           </button>
         )}
 
-        {/* Agents - desktop only */}
-        {!isMobile && onOpenAgents && (
-          <button
-            className="btn-icon"
-            onClick={onOpenAgents}
-            title="Manage Agents"
-            data-testid="agents-btn"
-          >
-            <Bot size={16} />
-          </button>
-        )}
-
         {/* Scripts - desktop only */}
         {!isMobile && onOpenScripts && onRunScript && (
           <QuickScriptsDropdown
@@ -524,18 +510,6 @@ export function Header({
               <GitHubLogo size={16} />
               <span>Import from GitHub</span>
             </button>
-            {/* Agents - in overflow on mobile */}
-            {onOpenAgents && (
-              <button
-                className="mobile-overflow-item"
-                onClick={() => handleOverflowAction(onOpenAgents)}
-                role="menuitem"
-                data-testid="overflow-agents-btn"
-              >
-                <Bot size={16} />
-                <span>Manage Agents</span>
-              </button>
-            )}
             {onOpenScripts && (
               <button
                 className="mobile-overflow-item"

packages/dashboard/app/components/__tests__/Header.test.tsx

@@ -643,20 +643,6 @@ describe("Header", () => {
       expect(screen.queryByTestId("overflow-project-selector-btn")).toBeNull();
     });
 
-    it("shows agents button in overflow menu on mobile when onOpenAgents provided", () => {
-      render(<Header onOpenSettings={vi.fn()} onOpenAgents={vi.fn()} />);
-      fireEvent.click(screen.getByTitle("More header actions"));
-      expect(screen.getByText("Manage Agents")).toBeDefined();
-    });
-
-    it("agents overflow menu item calls onOpenAgents when clicked", () => {
-      const onOpenAgents = vi.fn();
-      render(<Header onOpenSettings={vi.fn()} onOpenAgents={onOpenAgents} />);
-      fireEvent.click(screen.getByTitle("More header actions"));
-      fireEvent.click(screen.getByText("Manage Agents"));
-      expect(onOpenAgents).toHaveBeenCalledOnce();
-    });
-
     it("missions overflow menu item calls onOpenMissions when clicked", () => {
       const onOpenMissions = vi.fn();
       render(<Header onOpenSettings={vi.fn()} onOpenMissions={onOpenMissions} />);
@@ -682,36 +668,6 @@ describe("Header", () => {
     });
   });
 
-  // ── Agents Button ────────────────────────────────────────────────
-
-  it("renders agents button with correct title on desktop", () => {
-    const onOpenAgents = vi.fn();
-    render(<Header onOpenAgents={onOpenAgents} />);
-    const btn = screen.getByTitle("Manage Agents");
-    expect(btn).toBeDefined();
-  });
-
-  it("calls onOpenAgents when agents button is clicked", () => {
-    const onOpenAgents = vi.fn();
-    render(<Header onOpenAgents={onOpenAgents} />);
-    const btn = screen.getByTitle("Manage Agents");
-    fireEvent.click(btn);
-    expect(onOpenAgents).toHaveBeenCalledOnce();
-  });
-
-  it("does not render agents button when onOpenAgents is not provided", () => {
-    render(<Header />);
-    const btn = screen.queryByTitle("Manage Agents");
-    expect(btn).toBeNull();
-  });
-
-  it("agents button has correct data-testid", () => {
-    const onOpenAgents = vi.fn();
-    render(<Header onOpenAgents={onOpenAgents} />);
-    const btn = screen.getByTestId("agents-btn");
-    expect(btn).toBeDefined();
-  });
-
   // ── Multi-Project Selector ────────────────────────────────────
 
   it("shows ProjectSelector when 2+ projects provided", () => {