duct SIGINT during babs init / deploy loop doesn't abort cleanly

# duct SIGINT during babs init / deploy loop

Suspected root cause: duct doesn't handle Ctrl-C / SIGINT correctly.

deploy loops (1-anat/3-minimal) don't abort cleanly on Ctrl-C: `set +e`
around the duct call swallows the killed child (exit 137), marks the row
error, and CONTINUES to the next study. Add a SIGINT trap so Ctrl-C stops
the whole script. (Found 2026-06-01: Ctrl-C of duct on ds004636 -> marked
error -> loop started ds005256 -> partial.)

Related: babs-side `babs status --wait` SIGINT breadcrumb (same theme).

Start with the deploy loops named 1-anat and 3-minimal, focusing on the duct call and the surrounding set +e handling. Reproduce Ctrl-C during duct, then verify that SIGINT stops the whole script instead of marking the row as an error and continuing to the next study.

Written by the indexing model from the issue text.