blkreftable hardening (ee65441) came from fuzzing; the same treatment is missing as regression coverage. Add TAP tests that take real WAL summary files and backup manifests, apply systematic mutations (truncation at every structural boundary, bit flips in headers/length fields, oversized counts), and assert pg_walsummary / pg_verifybackup / incremental pg_basebackup fail with clean errors — never crash, never silently accept.
blkreftable hardening (ee65441) came from fuzzing; the same treatment is missing as regression coverage. Add TAP tests that take real WAL summary files and backup manifests, apply systematic mutations (truncation at every structural boundary, bit flips in headers/length fields, oversized counts), and assert pg_walsummary / pg_verifybackup / incremental pg_basebackup fail with clean errors — never crash, never silently accept.