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/app/dashboard/page.tsx

@@ -3,7 +3,7 @@
 import { useAtomValue } from "jotai";
 import { AlertCircle, Plus, Search } from "lucide-react";
 import { motion } from "motion/react";
-import { useRouter, useSearchParams } from "next/navigation";
+import { useRouter } from "next/navigation";
 import { useTranslations } from "next-intl";
 import { useEffect, useState } from "react";
 import { searchSpacesAtom } from "@/atoms/search-spaces/search-space-query.atoms";
@@ -89,7 +89,6 @@ function EmptyState({ onCreateClick }: { onCreateClick: () => void }) {
 
 export default function DashboardPage() {
 	const router = useRouter();
-	const searchParams = useSearchParams();
 	const [showCreateDialog, setShowCreateDialog] = useState(false);
 
 	const t = useTranslations("dashboard");
@@ -99,11 +98,12 @@ export default function DashboardPage() {
 		if (isLoading) return;
 
 		if (searchSpaces.length > 0) {
-			const params = searchParams.toString();
-			const query = params ? `?${params}` : "";
+			// Read the query string at the time of redirect — no subscription needed.
+			// (Vercel Best Practice: rerender-defer-reads 5.2)
+			const query = window.location.search;
 			router.replace(`/dashboard/${searchSpaces[0].id}/new-chat${query}`);
 		}
-	}, [isLoading, searchSpaces, router, searchParams]);
+	}, [isLoading, searchSpaces, router]);
 
 	// Show loading while fetching or while we have spaces and are about to redirect
 	const shouldShowLoading = isLoading || searchSpaces.length > 0;