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/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,