refactor(nav): extract the peek-open hook for reuse

The rail's hover/focus-to-peek logic — including the portal-proof focus tracking
(React-tree onFocus/onBlur plus a safety net for portals that unmount while
focused) — is about to be needed verbatim by the side panels. Lift it to
useHoverFocusWithin now that a second consumer exists. No behaviour change.

frontend/src/components/NavSidebar.tsx

@@ -30,6 +30,7 @@ import { getUnreadCount, subscribe } from "../lib/notifications";
 import type { Page } from "../lib/urlState";
 import { moduleLabelKey, moduleOrder, SYSTEM_PAGES } from "../lib/modules";
 import { useScrollFade } from "../lib/useScrollFade";
+import { useHoverFocusWithin } from "../lib/useHoverFocusWithin";
 import { type LangCode } from "../i18n";
 import AvatarImg from "./Avatar";
 import LanguageSwitcher from "./LanguageSwitcher";
@@ -62,37 +63,12 @@ export default function NavSidebar({
   onGoToFullHistory: () => void;
 }) {
   const { t } = useTranslation();
-  // Hover/focus expand: when unpinned, the rail sits slim (icons only) and expands to a labelled
-  // overlay on pointer hover or keyboard focus WITHOUT pushing content. Pinned keeps it expanded
-  // in-flow like before. `collapsed` (persisted per-account) now means "unpinned".
-  const [hovered, setHovered] = useState(false);
-  const [focused, setFocused] = useState(false);
-  // onFocus/onBlur (below) track focus through the REACT tree, so the rail's portaled menus
-  // (language switcher, account popover) count as "inside" and keep it open while you use them.
-  // The case they miss: a portal unmounts while focused, and browsers fire NO blur when a focused
-  // node is removed — focus silently falls to the body and `focused` would latch on forever.
-  // Safety net: whenever focus has landed nowhere, clear it. Deferred a tick so activeElement has
-  // settled, and rescheduled rather than queued — only the latest state matters.
-  useEffect(() => {
-    let timer: number | undefined;
-    const clearIfFocusLandedNowhere = () => {
-      const el = document.activeElement;
-      if (!el || el === document.body || el === document.documentElement) setFocused(false);
-    };
-    const soon = () => {
-      window.clearTimeout(timer);
-      timer = window.setTimeout(clearIfFocusLandedNowhere, 0);
-    };
-    document.addEventListener("focusout", soon);
-    document.addEventListener("click", soon);
-    return () => {
-      document.removeEventListener("focusout", soon);
-      document.removeEventListener("click", soon);
-      window.clearTimeout(timer);
-    };
-  }, []);
+  // When unpinned, the rail sits slim (icons only) and peeks open into a labelled overlay on hover
+  // or keyboard focus WITHOUT pushing content. Pinned keeps it expanded in-flow like before.
+  // `collapsed` (persisted per-account) now means "unpinned".
+  const peek = useHoverFocusWithin();
   const pinned = !collapsed;
-  const expanded = pinned || hovered || focused;
+  const expanded = pinned || peek.active;
   const slim = !expanded; // visual: icon-only rail
   const [acctOpen, setAcctOpen] = useState(false);
   const acctBtnRef = useRef<HTMLButtonElement | null>(null);
@@ -300,13 +276,8 @@ export default function NavSidebar({
     // Layout slot: reserves only the slim footprint when unpinned, so the expanded rail (below)
     // overlays content instead of pushing it. Pinned reserves the full width (in-flow).
     <div
+      {...peek.handlers}
       className={`relative shrink-0 transition-[width] ${pinned ? "w-[232px]" : "w-20"}`}
-      onMouseEnter={() => setHovered(true)}
-      onMouseLeave={() => setHovered(false)}
-      onFocus={() => setFocused(true)}
-      onBlur={(e) => {
-        if (!e.currentTarget.contains(e.relatedTarget as Node)) setFocused(false);
-      }}
     >
       <nav
         className={`glass absolute top-0 bottom-0 left-0 z-40 rounded-2xl flex flex-col py-3 m-3 transition-[width] ${

frontend/src/lib/useHoverFocusWithin.ts

@@ -0,0 +1,60 @@
+import { useEffect, useState, type FocusEvent } from "react";
+
+/**
+ * "Peek open on hover or keyboard focus" for a container — the shared brain behind the nav rail
+ * and the floating side panels, which sit slim until you point at them or tab into them.
+ *
+ * Spread `handlers` on the container; `active` is true while the pointer is over it (or any
+ * descendant) or focus is inside it.
+ *
+ * Focus is tracked through the REACT tree, so a portaled menu rendered by a child (the language
+ * switcher, the account popover) still counts as "inside" and holds the container open while you
+ * use it. The one case that misses: such a portal unmounts while focused, and browsers fire NO blur
+ * when a focused node is removed — focus silently falls to the body and `active` would latch on
+ * forever. Hence the document-level safety net: when focus has landed nowhere, clear it.
+ */
+export function useHoverFocusWithin(): {
+  active: boolean;
+  handlers: {
+    onMouseEnter: () => void;
+    onMouseLeave: () => void;
+    onFocus: () => void;
+    onBlur: (e: FocusEvent) => void;
+  };
+} {
+  const [hovered, setHovered] = useState(false);
+  const [focused, setFocused] = useState(false);
+
+  useEffect(() => {
+    let timer: number | undefined;
+    const clearIfFocusLandedNowhere = () => {
+      const el = document.activeElement;
+      if (!el || el === document.body || el === document.documentElement) setFocused(false);
+    };
+    // Deferred a tick so activeElement has settled, and rescheduled rather than queued — only the
+    // latest state matters.
+    const soon = () => {
+      window.clearTimeout(timer);
+      timer = window.setTimeout(clearIfFocusLandedNowhere, 0);
+    };
+    document.addEventListener("focusout", soon);
+    document.addEventListener("click", soon);
+    return () => {
+      document.removeEventListener("focusout", soon);
+      document.removeEventListener("click", soon);
+      window.clearTimeout(timer);
+    };
+  }, []);
+
+  return {
+    active: hovered || focused,
+    handlers: {
+      onMouseEnter: () => setHovered(true),
+      onMouseLeave: () => setHovered(false),
+      onFocus: () => setFocused(true),
+      onBlur: (e: FocusEvent) => {
+        if (!e.currentTarget.contains(e.relatedTarget as Node)) setFocused(false);
+      },
+    },
+  };
+}