Improve in-chat search discoverability and performance

[benjaminshafii]

Summary

Users can search chats globally with Cmd+Shift+F today, but feedback indicates chat search is not discoverable enough and could be easier when a user wants to search only within the current chat/session.

User feedback

chats should be searchable

Current behavior

• Cmd+Shift+F provides search, but users may not discover it.
• Search appears oriented around broader/global search rather than an obvious current-chat-only workflow.

Proposed improvements

• Add a more visible in-chat search affordance in the session UI.
• Make it easy to scope search to the current chat/session.
• Improve performance for large/long chats.
• Consider highlighting matches and providing next/previous navigation within the current chat.

Notes

This came from OpenWork app feedback on desktop 0.16.4.