Add a way to disable terminal mouse tracking (breaks native middle-click paste over SSH)

When running the Claude Code interactive TUI inside a terminal (Konsole/KDE tested),
the app appears to enable terminal mouse tracking/reporting (likely for scroll support).
This causes the terminal emulator to route all mouse events — including middle-click
paste (X11 PRIMARY selection) — to the claude process instead of handling them natively.

This breaks the normal "select text + middle-click to paste" workflow whenever the
active pane is running claude, which is especially noticeable when working over SSH
between two terminal sessions (one local, one SSH'd into a remote host running claude).

Workaround: holding Shift while clicking bypasses app mouse-reporting and restores
native terminal paste (standard xterm/Konsole convention), but this isn't discoverable
and shouldn't be required for basic clipboard usage.

Request: a flag (e.g. --no-mouse-tracking) or environment variable
(e.g. CLAUDE_CODE_DISABLE_MOUSE_TRACKING) to disable mouse capture in the TUI.

Environment: openSUSE Tumbleweed, KDE Plasma 6.6.5, Konsole, X11.