sys_columns and sys_tables were left out of the soft-delete conversion in
1786700003000. Their runtime models embed common.ModelTime, which is the
millisecond marker, so GORM queries them with deleted_at = 0 - against a
nullable datetime column holding NULL. Every row was invisible.
The repository carries two ModelTime types: the one under
cmd/migrate/migration/models still has a nullable gorm.DeletedAt and is
what builds the tables, while common/models has the marker and is what
queries them. Nothing connected the two, so a table could be built one
way and read the other with no signal at all.
The test now walks app/ for models embedding the marker and requires a
migration to cover each. tb_demo is exempt and says why: nothing reads it
at runtime.
