feat: Added scroll state support for chat-session-list navigation

[tiensi]

Summary
Added scroll state memory when navigating back from session view. This works for filtered search results as well.

Changes

• Added showSessionHistory to SessionsView to replace reliance on selectedSession being null
• Passed selectedSession as a new prop to SessionListView so that it can scroll to a selected session
• Added useEffect with MutationObserver to detect and scroll to selected session when loaded.

Request
#3664

After Changes

Screen.Recording.2025-08-26.at.2.03.27.PM.mov

NOTE
Previous PR was closed out due to staleness. Comments were addressed in this pr

[zanesq]

Thanks for doing this! Couple of notes:

1. It doesn't seem to respect the scroll after searching, it just goes back to the top when I hit back (see below). I don't think this is a blocker since the general back scroll position without search is a valuable feature but if that was the intent just wanted to point it out.

Kapture.2025-08-27.at.08.54.53.mp4

2. Using mutation observer is not ideal, we'd rather stick with react way of doing things. MutationObserver is typically a workaround for situations where you don’t have direct control over the DOM updates (such as with third-party libraries or dynamic content outside React’s control).

Can you change it to use refs instead something like

import React, { useEffect, useRef } from "react";

function SessionListView({ sessions, selectedSessionId, ...props }) {
  const sessionRefs = useRef({});

  useEffect(() => {
    if (selectedSessionId && sessionRefs.current[selectedSessionId]) {
      sessionRefs.current[selectedSessionId].scrollIntoView({
        block: "center",
        behavior: "smooth",
      });
    }
  }, [selectedSessionId, sessions]); // or filteredSessions if applicable

  return (
    <div>
      {sessions.map(session => (
        <Card
          key={session.id}
          ref={el => {
            // Store ref for each session card
            sessionRefs.current[session.id] = el;
          }}
          // ...other props
        >
          {/* ... */}
        </Card>
      ))}
    </div>
  );
}

[tiensi]

Thank you for the review! I'll go ahead and make your suggested changes.

It doesn't seem to respect the scroll after searching

I actually wanted to have a separate follow up to preserve the search-filter on back which would make it easier to reuse this scroller.

Using mutation observer is not ideal

Got it! I'm still getting a handle on react so I appreciate the heads up.

[tiensi]

I went ahead and pushed up the suggested changes:

• Replaced MutationObserver with useRef<Record<string, HTMLElement>>({});
• Kept scrollIntoView({block: "center"}) (there was a separate suggestion that smooth scroll experience is poor if a user scrolls all the way to the bottom and toggles back and forth)
• Updated useEffect to listen to [selectedSessionId, sessions] which should operate better with element ref.