M7 seed corpus: one file per fixture, `<fixture>.tsv` holding its row `fixture<TAB>source<TAB>expect`
(tests/hashjoin_m7.rs m7_seed_verdicts_and_pins reads every *.tsv here; column 1 must be the file's name).
- fixture: a decompose plan fixture id (plans/<id>.plan; regress-full-<stem> = plans/regress-full/<stem>.plan), or a
  fixtures/m7/<id>.plan (m7x-<n>: fixtures/m7/m7x.sql, captured by scripts/gravity-capture-plans.sh m7x).
- source: the census family (census/serve.tsv), or m7x/<join type> (left / semi / anti / right / full / right_semi /
  right_anti: m7_the_join_types checks the plan's hash-join type; chain: several probes on one pipeline); an m7x
  row with a PostgreSQL 18.6 golden (fixtures/m7/<id>.pg) is also judged by m7_rows_against_the_oracle.
- expect: the crate's lowering verdict: `served` (with its IR pin, LOWERV4_PIN=write after review), or
  `refused <text>`.
Re-keyed by fixture name (v5 core-face landing 8); the rows were first seeded per M7 kind / road (M7-RIG, 2026-09-27).
