perf: replace useSearchParams() with window.location.search in effects

Components were calling useSearchParams() at the top level but only
reading the value inside useEffect or callbacks, never in JSX. This
subscribed the entire component tree to every URL query change.

Fix: read from window.location.search directly inside the effect so
no React subscription is created.

Changes:
- new-chat/page.tsx: read commentId inside effect + popstate listener
  for SPA back/forward support; removes subscription from 1500+ line tree
- dashboard/page.tsx: read window.location.search at redirect time;
  removes searchParams from dep array
- public-chat-footer.tsx: one-shot mount read for action=clone param
- TokenHandler.tsx: one-shot mount read for token + refresh_token params

Implements Vercel React Best Practices Rule: rerender-defer-reads (5.2)

surfsense_web/components/public-chat/public-chat-footer.tsx

@@ -1,7 +1,7 @@
 "use client";
 
 import { Copy } from "lucide-react";
-import { useRouter, useSearchParams } from "next/navigation";
+import { useRouter } from "next/navigation";
 import { useCallback, useEffect, useRef, useState } from "react";
 import { toast } from "sonner";
 import { Button } from "@/components/ui/button";
@@ -15,7 +15,6 @@ interface PublicChatFooterProps {
 
 export function PublicChatFooter({ shareToken }: PublicChatFooterProps) {
 	const router = useRouter();
-	const searchParams = useSearchParams();
 	const [isCloning, setIsCloning] = useState(false);
 	const hasAutoCloned = useRef(false);
 
@@ -36,9 +35,11 @@ export function PublicChatFooter({ shareToken }: PublicChatFooterProps) {
 		}
 	}, [shareToken, router]);
 
-	// Auto-trigger clone if user just logged in with action=clone
+	// Auto-trigger clone if user just logged in with action=clone.
+	// Read from window.location.search on mount — no subscription needed since
+	// this is a one-time post-login check. (Vercel Best Practice: rerender-defer-reads 5.2)
 	useEffect(() => {
-		const action = searchParams.get("action");
+		const action = new URLSearchParams(window.location.search).get("action");
 		const token = getBearerToken();
 
 		// Only auto-clone once, if authenticated and action=clone is present
@@ -46,7 +47,7 @@ export function PublicChatFooter({ shareToken }: PublicChatFooterProps) {
 			hasAutoCloned.current = true;
 			triggerClone();
 		}
-	}, [searchParams, isCloning, triggerClone]);
+	}, [isCloning, triggerClone]);
 
 	const handleCopyAndContinue = async () => {
 		const token = getBearerToken();