Matrix coverage: stop hand-maintaining the per-type snapshot list in CI

[tobyhede]

Problem

Adding a scalar encrypted-domain type currently requires a manual edit to CI that is easy to forget. The matrix-coverage job in .github/workflows/test-eql.yml hardcodes the snapshot files it diffs:

# .github/workflows/test-eql.yml  (matrix-coverage job)
- name: Regenerate and verify the matrix test-name inventory
  run: |
    mise run test:matrix:inventory
    git diff --exit-code -- tests/sqlx/snapshots/int4_matrix_tests.txt \
                            tests/sqlx/snapshots/int2_matrix_tests.txt \
      || { echo "Coverage inventory stale — run 'mise run test:matrix:inventory' and commit."; exit 1; }

The same per-type hardcoding exists in the test:matrix:inventory task in mise.toml, which has one grep '^scalars::<T>' ... > snapshots/<T>_matrix_tests.txt block per type.

So every new type (int8, bool, date, …) means editing two places:

    git diff --exit-code -- tests/sqlx/snapshots/int4_matrix_tests.txt \
                            tests/sqlx/snapshots/int2_matrix_tests.txt \
                            tests/sqlx/snapshots/int8_matrix_tests.txt \   # <-- easy to forget

If either edit is forgotten, the new type's snapshot is silently not coverage-gated — which is exactly the failure mode this job exists to prevent.

Asks

1. Abstract the per-type list so the extra step isn't required. Enumerate the scalar types dynamically from tasks/codegen/types/*.toml (the single source of truth) instead of hand-listing snapshot files — in both test:matrix:inventory (mise.toml) and the CI diff step. This is the same enumeration mise run codegen:domain:all and mise run fixture:generate:all already use, so adding a type is picked up automatically with no CI/task edit.

2. Add a check that catches types with no snapshot. Fail CI if a type manifest (with a [fixture]/matrix surface) has no committed tests/sqlx/snapshots/<T>_matrix_tests.txt, and ideally the converse (a snapshot with no manifest — i.e. a removed type left a stale snapshot). Today a missing snapshot is simply uncovered rather than a hard error.

Prior art in this repo

fixture:generate:all (tasks/fixtures.toml) and codegen:domain:all (mise.toml) already enumerate tasks/codegen/types/*.toml and act on every type. The matrix-coverage inventory should follow the same pattern so the type list lives in exactly one place.