Switching folders in UI causes confusing session loss - no warning, hard to recover

Summary

When using the Claude Code UI to open a new folder, the previous session becomes inaccessible without knowing to press A in the /resume picker. This creates a very frustrating experience where users believe they've lost all their work.

Steps to Reproduce

1. Start Claude Code in folder A
2. Work on a substantial session (hours of context, many interactions)
3. Click the folder icon in the UI and select a different folder B
4. Try to get back to your previous session

Expected Behavior

• Warning before switching folders: "This will switch to a new session. Your current session will be saved and can be resumed later."
• Clear indication of how to get back to previous sessions
• The /resume picker should default to showing recent sessions across all projects, or at minimum clearly indicate that pressing A shows more sessions

Actual Behavior

• Session switches immediately with no warning
• Previous session appears to be "gone"
• /resume only shows sessions from current directory by default
• User must know to press A to see "all projects" - this is not discoverable
• Quitting and restarting loses folder context

Impact

• Users lose hours of work context
• Very frustrating and trust-breaking experience
• Users may not realize their session still exists in ~/.claude/projects/

Suggested Fixes

1. Add confirmation dialog when switching folders: "Switch to [folder]? Your current session will be saved."
2. Show recent sessions from all projects in /resume by default, or add a "Recent" section at the top
3. Add visual indicator in the picker showing that A toggles project scope
4. Remember last working directory when restarting Claude Code
5. Add "Return to previous session" option after switching folders

Additional Issue: Mac App and Terminal Not Synced

When resuming a session via terminal (claude --resume <session-id>), the session does not appear in the Mac app. The two interfaces appear to have separate session state:

• Session restored successfully in terminal
• Same session not visible in Mac app
• No way to "transfer" or sync the session to the Mac app

This creates further confusion - users may have Claude Code open in the Mac app but need to use terminal commands to recover sessions, and then can't get those sessions back into the app they're actually using.

Environment

• Claude Code version: 2.0.65
• Platform: macOS Darwin 25.2.0

Additional Context

Session files are preserved in ~/.claude/projects/ but the UI makes them effectively invisible. The workaround (pressing A in the resume picker) is not discoverable through normal usage.