do_seed fills foreign-key columns by sampling existing parent rows
(D14): sample_parent_key_tuples reads distinct parent keys, and a
compound FK reads all its child columns from one sampled parent row per
child row. An empty parent is refused with a friendly "seed the parent
first" error. The block guard (D1) refuses a NOT NULL blob column (seed
can't generate one); a nullable blob is omitted (-> NULL).
4 integration tests (valid FK references, empty-parent refusal, NOT NULL
blob refusal, nullable-blob omission). 2331 pass / 0 fail / 0 skip,
clippy all-targets clean.
Deferred to P1.3b: identifier/constraint uniqueness incl. junction
distinct-combos (D10), IN-CHECK derivation (D17), dedicated SeedResult +
capped preview (D18) + advisory (D12/D13), and the multi-row path.
claude@clouddev1
73493fa68b