A debounced `[ERR]` / `[WRN]` marker at the right edge of
the input row, summarising — before submit — whether the
current command would run. Backed by a small
diagnostics-severity model: the walker emits severity-
tagged diagnostics (parse outcome, schema-existence of
table / column names) that the indicator summarises and
the existing highlighting / hint layers detail. Advisory
only — submission is never blocked.
- docs/adr/0027-input-validity-indicator.md — the ADR.
- docs/adr/README.md — index entry.
- docs/requirements.md — new S6 (TUI shell).
claude@clouddev1