Function cpu_gaps

fn cpu_gaps(project: &Project) -> String

What this export cannot render, as a suffix for the progress line (empty when nothing is dropped).

ponytail: export renders on a background thread with the CPU Compositor; the GL context lives on the UI thread, so GPU-only effect kinds and node graphs are skipped. Naming them in the status beats dropping them silently — replace this with a real GPU render path (GpuRenderer::render_frame fed from the UI thread) and the note goes away.