LIKE phone_ranges INCLUDING DEFAULTS copied the serial id default pointing
at the original sequence, which atomic-swap destroys (DROP phone_ranges_old
CASCADE) after the first import — the second import then hit NOT NULL on
staging.id. Now staging gets a dedicated sequence named by import_id, OWNED
BY the id column so it travels on RENAME and drops with the old table.
Reproduced via a post-swap test (live id default removed).