👐 fix: Open/Close Sidebar Button Animation UX Regression from #10521 (#10694)

Problem:
--------
Commit 5ed1f2991 introduced a layout shift regression when opening the
sidebar. The UI would visibly "jump" as elements shifted right before
the animation completed. Closing the sidebar worked correctly.

Root Cause Analysis:
--------------------
The accessibility PR added a redundant `{navVisible && ...}` conditional
wrapper around the `<nav>` content inside Nav.tsx's `motion.div`. This
caused a race condition:

1. User clicks "Open Sidebar" button
2. `navVisible` state becomes `true`
3. React renders the `motion.div` AND its children simultaneously
4. The inner `{navVisible && (<nav>...)}` renders content at full width
   (320px/260px) BEFORE framer-motion applies `initial={{ width: 0 }}`
5. Brief flash of full-width content causes visible layout shift
6. Animation then starts from width: 0, but damage is done

The ref-based focus management (passing `openSidebarRef`/`closeSidebarRef`
through context) was suspected but was not the actual cause. However,
`requestAnimationFrame` focus calls during animation start could trigger
forced layout calculations, exacerbating the issue.

Solution:
---------
1. Remove redundant conditional rendering in Nav.tsx
   - The outer `{navVisible && (<motion.div>...)}` already controls
     visibility
   - The `overflow-x-hidden` class on motion.div clips content during
     animation
   - Content should always exist inside motion.div for smooth clipping

2. Replace ref-based focus with ID-based focus management
   - Refs passed through component tree can affect React's reconciliation
   - Using `document.getElementById()` decouples focus from render cycle
   - Exported `CLOSE_SIDEBAR_ID` and `OPEN_SIDEBAR_ID` constants for
     consistency

3. Delay focus until after animation completes
   - Changed from `requestAnimationFrame` to `setTimeout(..., 250)`
   - Animation duration is 200ms; 250ms ensures completion
   - Prevents layout thrashing during animation

4. Clean up prop drilling
   - Removed `openSidebarRef`/`closeSidebarRef` from Root.tsx context
   - Simplified Nav.tsx, Header.tsx, NewChat.tsx prop signatures
   - Updated ContextType to remove ref properties

Files Changed:
--------------
- client/src/routes/Root.tsx
- client/src/components/Nav/Nav.tsx
- client/src/components/Nav/NewChat.tsx
- client/src/components/Chat/Header.tsx
- client/src/components/Chat/Menus/OpenSidebar.tsx
- client/src/common/types.ts

Accessibility Note:
-------------------
The original inner conditional was added to prevent keyboard navigation
to hidden sidebar content for screen readers. This is still handled by:
- AnimatePresence unmounting the motion.div after exit animation
- The motion.div having width: 0 during exit (content not reachable)
- Screen readers typically skip content being animated out
- Other: removed non-existant prop from BookmarkNav

Testing:
--------
- Verified smooth animation when opening sidebar (no layout shift)
- Verified smooth animation when closing sidebar (unchanged)
- Verified focus transfers correctly between open/close buttons
- Verified keyboard navigation works as expected

client/src/components/Nav/Nav.tsx

@@ -50,13 +50,9 @@ const Nav = memo(
   ({
     navVisible,
     setNavVisible,
-    openSidebarRef,
-    closeSidebarRef,
   }: {
     navVisible: boolean;
     setNavVisible: React.Dispatch<React.SetStateAction<boolean>>;
-    openSidebarRef?: React.RefObject<HTMLButtonElement>;
-    closeSidebarRef?: React.RefObject<HTMLButtonElement>;
   }) => {
     const localize = useLocalize();
     const { isAuthenticated } = useAuthContext();
@@ -170,7 +166,7 @@ const Nav = memo(
             <>
               <div className="mt-1.5" />
               <Suspense fallback={null}>
-                <BookmarkNav tags={tags} setTags={setTags} isSmallScreen={isSmallScreen} />
+                <BookmarkNav tags={tags} setTags={setTags} />
               </Suspense>
             </>
           )}
@@ -211,36 +207,32 @@ const Nav = memo(
             >
               <div className="h-full w-[320px] md:w-[260px]">
                 <div className="flex h-full flex-col">
-                  {navVisible && (
-                    <nav
-                      id="chat-history-nav"
-                      aria-label={localize('com_ui_chat_history')}
-                      className="flex h-full flex-col px-2 pb-3.5 md:px-3"
-                    >
-                      <div className="flex flex-1 flex-col" ref={outerContainerRef}>
-                        <MemoNewChat
-                          subHeaders={subHeaders}
-                          toggleNav={toggleNavVisible}
-                          headerButtons={headerButtons}
-                          isSmallScreen={isSmallScreen}
-                          openSidebarRef={openSidebarRef}
-                          closeSidebarRef={closeSidebarRef}
-                        />
-                        <Conversations
-                          conversations={conversations}
-                          moveToTop={moveToTop}
-                          toggleNav={itemToggleNav}
-                          containerRef={listRef}
-                          loadMoreConversations={loadMoreConversations}
-                          isLoading={isFetchingNextPage || showLoading || isLoading}
-                          isSearchLoading={isSearchLoading}
-                        />
-                      </div>
-                      <Suspense fallback={null}>
-                        <AccountSettings />
-                      </Suspense>
-                    </nav>
-                  )}
+                  <nav
+                    id="chat-history-nav"
+                    aria-label={localize('com_ui_chat_history')}
+                    className="flex h-full flex-col px-2 pb-3.5 md:px-3"
+                  >
+                    <div className="flex flex-1 flex-col" ref={outerContainerRef}>
+                      <MemoNewChat
+                        subHeaders={subHeaders}
+                        toggleNav={toggleNavVisible}
+                        headerButtons={headerButtons}
+                        isSmallScreen={isSmallScreen}
+                      />
+                      <Conversations
+                        conversations={conversations}
+                        moveToTop={moveToTop}
+                        toggleNav={itemToggleNav}
+                        containerRef={listRef}
+                        loadMoreConversations={loadMoreConversations}
+                        isLoading={isFetchingNextPage || showLoading || isLoading}
+                        isSearchLoading={isSearchLoading}
+                      />
+                    </div>
+                    <Suspense fallback={null}>
+                      <AccountSettings />
+                    </Suspense>
+                  </nav>
                 </div>
               </div>
             </motion.div>