refactor: dedupe FootprintPlotter, import from cs_util

[cailmdaley]

Summary

FootprintPlotter was duplicated between sp_validation.plots and cs_util.plots, with the local copy stale relative to the canonical cs_util version. Delete the sp_validation copy and re-export cs_util's class so the public surface (from sp_validation.plots import FootprintPlotter) is unchanged.

What diverged

The sp_validation copy was missing improvements that had landed in cs_util:

• no vmin kwarg on plot_area / _regions
• no draw_milky_way call
• no set_autorescale(False) + set_extent(extend) enforcement
• no axis labels set on the projection

Both versions share the same __init__ signature (nside_coverage=32, nside_map=2048) and the same public methods (create_hsp_map, plot_area, plot_region, plot_all_regions, plot_footprint_as_hp, hp_pixel_centers). cs_util's API is a superset; nothing removed.

Backward compatibility

FootprintPlotter is re-imported at module top level in sp_validation/plots.py, so every existing import path keeps working:

• from sp_validation.plots import FootprintPlotter — still works
• from sp_validation.cosmo_val import FootprintPlotter — still works (via cosmo_val's own re-import)
• from sp_validation.plots import * — still picks it up

Caller audit

Grepped the repo for FootprintPlotter; every caller was inspected:

• src/sp_validation/cosmo_val.py:1011 — FootprintPlotter() + create_hsp_map + plot_region(hsp_map, fp._regions[region], outpath=...). Compatible.
• notebooks/demo_create_footprint_mask.py:95 — same usage via cosmo_val.FootprintPlotter(). Compatible.
• notebooks/cosmo_val/catalog_paper_plot/plot_gaia_sky.py:100,138 — FootprintPlotter(nside_coverage=32, nside_map=2048) and plot_area(..., vmax=...). vmax is still a keyword arg in cs_util's signature. Compatible.

No caller passes vmax to __init__ (the stale class didn't accept it either); no caller assumes autorescale=True; no caller reads _regions[*] expecting the absence of vmin.

Visual deltas to expect

Callers will now see the cs_util improvements on footprint plots: the Milky Way overlay, axis labels, and enforced extents. Color scaling will start at vmin=0 rather than matplotlib auto, which matches the implicit previous behavior for count maps.

Other changes

• pyproject.toml: bumped cs_util>=0.1.5 to cs_util>=0.1.9 to guarantee the import resolves.

Test plan

• Re-run cosmo_val.CosmoVal.plot_footprints and confirm NGC/SGC/fullsky plots render.
• Re-run notebooks/cosmo_val/catalog_paper_plot/plot_gaia_sky.py end-to-end.
• Confirm from sp_validation.plots import FootprintPlotter and from sp_validation.cosmo_val import FootprintPlotter resolve to the cs_util class.

Generated with Claude Code (Opus 4.7, 1M context).

[cailmdaley]

Live smoke test passed inside the shapepipe container (Python 3.12, cs_util 0.1.9):

from sp_validation.plots import FootprintPlotter
import cs_util.plots
fp = FootprintPlotter()
# FootprintPlotter.__module__ -> cs_util.plots
# FootprintPlotter is cs_util.plots.FootprintPlotter -> True
# list(fp._regions.keys()) -> ['NGC', 'SGC', 'fullsky']
# all('vmin' in r for r in fp._regions.values()) -> True

Re-export is transparent; same class object is returned, _regions matches cs_util's (with vmin). Ready for review.