fix(dashboard): close SSE connections on outbound backpressure

The global SSE broadcast called res.write() without checking the return
value, so a paused or backgrounded client would silently accumulate
every store event for every entity (tasks, missions, plugins, agents,
chat, ...) into res.outputData until the dashboard process OOMed.
Add a 4 MB writableLength threshold; when exceeded, tear down the
connection so the OS releases the buffer.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/dashboard/app/hooks/__tests__/useViewState.test.ts

@@ -17,6 +17,7 @@ const PROJECT: ProjectInfo = {
 function createOptions(overrides: Partial<Parameters<typeof useViewState>[0]> = {}): Parameters<typeof useViewState>[0] {
   return {
     projectsLoading: false,
+    projectsError: null,
     currentProjectLoading: false,
     currentProject: null,
     projectsLength: 1,
@@ -189,6 +190,29 @@ describe("useViewState", () => {
     vi.useRealTimers();
   });
 
+  it("does NOT call openSetupWizard when the initial projects fetch failed", async () => {
+    vi.useFakeTimers();
+    const openSetupWizard = vi.fn();
+
+    renderHook(() =>
+      useViewState(
+        createOptions({
+          projectsLength: 0,
+          currentProject: null,
+          projectsError: "Failed to fetch projects",
+          openSetupWizard,
+        }),
+      ),
+    );
+
+    await act(async () => {
+      vi.advanceTimersByTime(500);
+    });
+
+    expect(openSetupWizard).not.toHaveBeenCalled();
+    vi.useRealTimers();
+  });
+
   // ── Insights view persistence ─────────────────────────────────────
 
   it("reads saved insights taskView from scoped localStorage on init", async () => {

packages/dashboard/app/hooks/useViewState.ts

@@ -32,6 +32,7 @@ function normalizeTaskView(value: TaskView): TaskView {
 
 interface UseViewStateOptions {
   projectsLoading: boolean;
+  projectsError: string | null;
   currentProjectLoading: boolean;
   currentProject: ProjectInfo | null;
   projectsLength: number;
@@ -53,6 +54,7 @@ export interface UseViewStateResult {
 export function useViewState(options: UseViewStateOptions): UseViewStateResult {
   const {
     projectsLoading,
+    projectsError,
     currentProjectLoading,
     currentProject,
     projectsLength,
@@ -112,6 +114,7 @@ export function useViewState(options: UseViewStateOptions): UseViewStateResult {
   useEffect(() => {
     if (projectsLoading || currentProjectLoading) return;
     if (setupWizardOpen) return;
+    if (projectsError) return;
     if (projectsLength > 0 || currentProject) return;
 
     const timer = window.setTimeout(() => {
@@ -121,6 +124,7 @@ export function useViewState(options: UseViewStateOptions): UseViewStateResult {
     return () => window.clearTimeout(timer);
   }, [
     projectsLoading,
+    projectsError,
     projectsLength,
     currentProjectLoading,
     currentProject,