Claude Code desktop app gets detachable, multi-window panes

Anthropic's Claude Code desktop app now lets you pop any pane, the diff view or the terminal, out into its own separate window. You can drag it to a second monitor while Claude keeps working in the main window, then dock it back later, and you can also arrange multiple sessions side by side or stacked on one screen.

This builds on other recent desktop changes: the app previously gained a `/resume` command that picks up sessions started from the terminal, so the underlying push has been toward letting the desktop app and CLI share state and screen space more fluidly rather than treating them as separate tools.