fix: eliminate setState-in-effect anti-patterns (Category D, #200)

app/auth/error/page.tsx

@@ -36,9 +36,8 @@ function ErrorContent() {
   useEffect(() => {
     if (!isTransient || retryCount >= MAX_RETRIES || retrying) return;
     if (countdown <= 0) {
-      setRetryCount((c) => c + 1);
-      retry();
-      return;
+      const id = setTimeout(() => retry(), 0);
+      return () => clearTimeout(id);
     }
     const timer = setTimeout(() => setCountdown((c) => c - 1), 1000);
     return () => clearTimeout(timer);

app/page.tsx

@@ -17,20 +17,13 @@ type FilterType = "public" | "private" | "mine" | "all";
 
 export default function HomePage() {
   const { data: session, status } = useSession();
-  const [filter, setFilter] = useState<FilterType>("public");
+  const [userFilter, setUserFilter] = useState<FilterType | null>(null);
   const [searchQuery, setSearchQuery] = useState("");
   const [debouncedSearch, setDebouncedSearch] = useState("");
 
   const isAuthenticated = status === "authenticated";
-
-  // Default authenticated users to "mine" tab
-  const authDefaultApplied = useRef(false);
-  useEffect(() => {
-    if (!authDefaultApplied.current && status !== "loading") {
-      authDefaultApplied.current = true;
-      if (isAuthenticated) setFilter("mine");
-    }
-  }, [status, isAuthenticated]);
+  const filter = userFilter ?? (status !== "loading" && isAuthenticated ? "mine" : "public");
+  const setFilter = useCallback((f: FilterType) => setUserFilter(f), []);
 
   // Debounce search input
   const debounceRef = useRef<ReturnType<typeof setTimeout> | null>(null);

app/settings/page.tsx

@@ -330,16 +330,17 @@ function EditorPreferencesSection() {
   const setTheme = useEditorModeStore((s) => s.setTheme);
   const preferEditMode = useEditorModeStore((s) => s.preferEditMode);
   const setPreferEditMode = useEditorModeStore((s) => s.setPreferEditMode);
-  const [highlightedSetting, setHighlightedSetting] = useState<string | null>(null);
+  const [highlightedSetting, setHighlightedSetting] = useState<string | null>(() => {
+    if (typeof window === "undefined") return null;
+    return window.location.hash.slice(1) || null;
+  });
 
-  // Highlight and scroll to the setting referenced by the URL hash
+  // Scroll to the setting referenced by the URL hash and clear the highlight after 2 s
   useEffect(() => {
     const hash = window.location.hash.slice(1);
     if (!hash) return;
     const el = document.getElementById(hash);
-    if (!el) return;
-    el.scrollIntoView({ behavior: "smooth", block: "center" });
-    setHighlightedSetting(hash);
+    if (el) el.scrollIntoView({ behavior: "smooth", block: "center" });
     const timer = setTimeout(() => setHighlightedSetting(null), 2000);
     return () => clearTimeout(timer);
   }, []);

components/editor/shared/EntityTreeToolbar.tsx

@@ -1,6 +1,6 @@
 "use client";
 
-import { useRef, useCallback, useState, useEffect } from "react";
+import { useRef, useCallback, useState } from "react";
 import { Search, X, Plus, ChevronDown, ChevronsDown, ChevronRight, ChevronsRight, Loader2 } from "lucide-react";
 import { cn } from "@/lib/utils";
 
@@ -44,17 +44,13 @@ export function EntityTreeToolbar({
   const internalRef = useRef<HTMLInputElement>(null);
   const inputRef = searchInputRef || internalRef;
 
-  // Dismissible tip
-  const [showTip, setShowTip] = useState(false);
-  useEffect(() => {
+  const [showTip, setShowTip] = useState(() => {
     try {
-      if (!localStorage.getItem(TIP_DISMISSED_KEY)) {
-        setShowTip(true);
-      }
+      return !localStorage.getItem(TIP_DISMISSED_KEY);
     } catch {
-      // localStorage unavailable
+      return false;
     }
-  }, []);
+  });
 
   const dismissTip = useCallback(() => {
     setShowTip(false);