Add hubble_ultra_deep_field() Source template

[astronomyk]

note: this is most definitely a throw-away function because it's based on the flawed use of predetermined sersic profiles. The scopesim_targets way of doing things is vastly superior. But we need to work out how to build that bridge...

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Builds a single scopesim.Source aggregating thousands of Sersic-profile galaxies that mimic the HUDF: positions, sizes, Sersic indices, axis ratios, redshifts and F160W magnitudes come from a vendored cross-match of Skelton+2014 (3D-HST, J/ApJS/214/24) with van der Wel+2012 H-band GALFIT fits (J/ApJS/203/24), trimmed to a 2-arcmin cone around the HUDF centre and m_F160W < 28.

Per-galaxy SEDs are assigned by a Sersic-index cut (n > 2.5 -> early, defaulting to Brown+2014 NGC0584; else late-type, defaulting to NGC4254). Each row is rendered via the existing
extragalactic.galaxy() function; sub-sources are summed into one Source.

• scopesim_templates/extragalactic/deep_field.py: public API.
• scopesim_templates/extragalactic/_make_hudf_catalogue.py: off-tree Vizier ingest + cross-match + trim script that produced the vendored FITS (re-run only to refresh the data).
• scopesim_templates/extragalactic/data/hudf_catalogue.fits: vendored 2378-row catalogue (168 kB).
• scopesim_templates/tests/test_extragalactic/test_deep_field.py: 7 webtest-marked tests covering Source return, counts, FOV cuts, early/late split, amplitude pass-through, mag limit, custom path.
• scopesim_templates/tests/test_extragalactic/data/toy_hudf.fits: 3-row fixture used by all tests so they don't depend on the full catalogue.
• scopesim_templates/tests/visual_inspection/plot_hubble_ultra_deep_field.py
  • hubble_ultra_deep_field.png: visual-inspection script that paints the per-galaxy stamps onto a shared WCS-aligned canvas, scaled by 10^(-0.4*mag), and the baseline PNG it produces.
• .gitignore: carve-out exceptions for the new data/ directories.

[codecov]

Codecov Report

❌ Patch coverage is 47.00855% with 62 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.15%. Comparing base (f08fb1d) to head (d2987cf).

Files with missing lines	Patch %	Lines
...im_templates/extragalactic/_make_hudf_catalogue.py	18.66%	61 Missing ⚠️
scopesim_templates/extragalactic/deep_field.py	97.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #183      +/-   ##
==========================================
- Coverage   77.09%   75.15%   -1.94%     
==========================================
  Files          34       36       +2     
  Lines        1698     1815     +117     
==========================================
+ Hits         1309     1364      +55     
- Misses        389      451      +62     

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