[Feature Request] Display indicator when session is already open in another terminal

Feature Request: Session Lock Indicator for Claude Code Resume

Description

When resuming a Claude Code session, display a clear indicator if the session is already open in another terminal. This would help prevent accidental duplicate sessions and conflicts when working with multiple terminal windows.

Current Behavior

Currently, when attempting to resume a session that's already active in another terminal, the user receives lock acquisition errors without clear visibility into the conflict.

Desired Behavior

When resuming a session, show a warning or indicator if:

• The session is already active in another terminal
• The lock file is held by another process
• Allow the user to choose to either connect to the existing session or forcefully take over the lock

Environment

• Platform: macOS (darwin)
• Terminal: VS Code
• Version: 2.1.78

Benefits

• Prevents accidental session conflicts
• Improves user awareness of multi-terminal sessions
• Reduces confusing error messages
• Provides clearer workflow for resuming sessions