Add support for concurrency via threads to fs mode

[maddenp-cu]

Synopsis

Add support for concurrency via threads to fs mode. Underlying iotaa supports threads, so this is just a matter of collecting the requested number of threads from CLI or API users and passing it on. Given a config.yaml specifying 3 GFS forecast GRIB files to download...

Old single-threaded behavior:

$ time uw fs copy -c config.yaml --target-dir ./grib
[2026-02-11T05:16:29]     INFO Validating config against internal schema: files-to-stage
[2026-02-11T05:16:29]     INFO Schema validation succeeded for fs config
[2026-02-11T05:16:29]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f001 -> grib/gfs.t12z.pgrb2.0p25.f001: Executing
[2026-02-11T05:16:51]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f001 -> grib/gfs.t12z.pgrb2.0p25.f001: Ready
[2026-02-11T05:16:51]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f002 -> grib/gfs.t12z.pgrb2.0p25.f002: Executing
[2026-02-11T05:17:21]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f002 -> grib/gfs.t12z.pgrb2.0p25.f002: Ready
[2026-02-11T05:17:21]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f003 -> grib/gfs.t12z.pgrb2.0p25.f003: Executing
[2026-02-11T05:17:47]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f003 -> grib/gfs.t12z.pgrb2.0p25.f003: Ready
[2026-02-11T05:17:47]     INFO File copies: Ready

real    1m19.354s
user    0m4.100s
sys     0m2.402s

New behavior, with three threads:

$ time uw fs copy -c config.yaml --target-dir ./grib --threads 3
[2026-02-11T05:17:58]     INFO Validating config against internal schema: files-to-stage
[2026-02-11T05:17:58]     INFO Schema validation succeeded for fs config
[2026-02-11T05:17:58]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f001 -> grib/gfs.t12z.pgrb2.0p25.f001: Executing
[2026-02-11T05:17:58]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f002 -> grib/gfs.t12z.pgrb2.0p25.f002: Executing
[2026-02-11T05:17:58]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f003 -> grib/gfs.t12z.pgrb2.0p25.f003: Executing
[2026-02-11T05:18:30]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f003 -> grib/gfs.t12z.pgrb2.0p25.f003: Ready
[2026-02-11T05:18:31]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f001 -> grib/gfs.t12z.pgrb2.0p25.f001: Ready
[2026-02-11T05:18:35]     INFO HTTP https://nomads.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.20260209/12/atmos/gfs.t12z.pgrb2.0p25.f002 -> grib/gfs.t12z.pgrb2.0p25.f002: Ready
[2026-02-11T05:18:35]     INFO File copies: Ready

real    0m36.939s
user    0m4.200s
sys     0m2.316s

So, a reduction from 1m19s to 0m37s.

Type

• Documentation
• Enhancement (adds new functionality)

Impact

• This is a non-breaking change (existing functionality continues to work as expected)

Checklist

• I have added myself and any co-authors to the PR's Assignees list.
• I have reviewed the documentation and have made any updates necessitated by this change.