Duct-wrap each iterate step

Per the project's "wrap runs in duct" convention, wrap each `iterate` sub-step in duct: `duct -p logs/_/-...` for step ∈ {select, merge-config, babs-init, pin-inclusion, babs-submit, babs-merge}. Decide whether `logs/` is tracked or gitignored (lean tracked).

Locate the iterate entry point and inspect how the select, merge-config, babs-init, pin-inclusion, babs-submit, and babs-merge sub-steps currently run, along with the project's existing duct-wrapping convention. Confirm whether logs/ is tracked or gitignored, then verify that every listed step produces the requested logs/_/-... path and that the iterate flow still completes.

Written by the indexing model from the issue text.