`export --format csv` produces missing newlines between rows when table scan spans multiple pages

[YN-CTC]

When using dy export --format csv (with --keys-only or --attributes) on a table large enough to require multiple DynamoDB Scan pages, some rows in the output CSV file are missing the newline separator between them.

Steps to Reproduce

1. Have a DynamoDB table with more items than a single Scan page can return (typically > ~400 items depending on item size)

2. Run:

   dy export --format csv --keys-only -o output.csv

3. Inspect output.csv

Expected Behavior

Every row is separated by a newline:

"item1_1","item1_2"
"item2_1","item2_2"
"item3_1","item3_2"
"item4_1","item4_2"

Actual Behavior

At Scan page boundaries, two rows are concatenated on the same line (missing newline):

"item1_1","item1_2"
"item2_1","item2_2""item3_1","item3_2"
"item4_1","item4_2"