On Linux, `arboard::Clipboard::new()` opens a blocking connect() to the
X11 Unix socket. When no X server is running (headless, WSL2 without
WSLg), the call hangs indefinitely. Because raw mode and the alternate
screen are already active at that point, Ctrl+C no longer generates
SIGINT and the event loop hasn't started yet — leaving the user with a
blank screen and no way to exit.
Move clipboard initialization from `ClipboardHandler::new()` (called
synchronously during App construction) to a lazy `ensure_clipboard()`
that runs on first read/write with a 500 ms timeout. If the X11
connection doesn't respond in time, the handler stays in fallback mode
and `write_text` falls through to the existing OSC 52 / pbcopy /
PowerShell paths.
jayzhu
5c452328ab