[Feature Request] Add session ID retrieval command for interactive sessions

Currently, there's no straightforward way to retrieve a session ID from an active Claude Code session, which severely limits the utility of the claude -r "<session-id>" resume command. Users need the session ID to resume conversations later, but have no way to obtain it during an interactive session.

Problem: Without access to the session ID, the resume functionality becomes nearly impossible to use effectively, especially for long-running projects where you might want to return to a specific session days or weeks later.

Proposed Solutions:

1. Add session ID to interactive commands: Introduce a new command (e.g., /session) or extend the existing /status command to display the current session ID during an active Claude Code session.
2. Enhance the session list view: Include the session ID as a column in the claude -r table output, making it easy to copy and reference for future use.

These changes would make session management much more practical and allow developers to effectively pause and resume their work across multiple sessions.

Related to #1335