zwp_input_method_v2 in one new file, with its popup, drawn from the reply
the engine already produced; the session picks the popup, so the engine,
the IPC and the X11 side are untouched. Records what was measured, what
fcitx5 does differently and why, and what was refused.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
