cba5e829fc
Maintainer-reported (handoff): after spawning a sub-agent in YOLO, the transcript renders solid black and scroll keys go dead, but footer + sidebar still render fine. The shape (black + dead input together) strongly suggests a `View` is on the stack that returns empty layout AND intercepts key events at the top level. The fix wants a tighter repro than we have today. Add `tracing::debug!` to every push / push_boxed / pop on `ViewStack` and to the implicit pops in `apply_action` (Close + EmitAndClose). Each line carries the `ModalKind` and post-action depth, so a future `RUST_LOG=deepseek_tui::view_stack=debug` capture will show exactly which view stayed pushed when the symptom recurred. No behavior change. The handoff explicitly suggested this as the first-look diagnostic step; we ship the diagnostic now so the next report comes with evidence. Refs the unresolved sub-agent black-transcript symptom captured in session-3 handoff. Will surface to a tracking issue once we have a concrete repro from the maintainer. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>