The helper TRUNCATEd papers CASCADE and only then ran ingest_all.sh, which
failed on the missing chunks.section column (audit M-1) — leaving the corpus
wiped. Add a preflight that verifies chunks.section exists BEFORE the
destructive step and aborts early (no TRUNCATE) with the owner-level ALTER to
run, since the app user cannot alter postgres-owned tables.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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