Docs, tests, and CI: API reference, unit test coverage, and documentation updates

[charliekilpatrick]

Description

This PR merges the dev branch into main, bringing in Sphinx API documentation, a larger unit test suite with integration markers, CI/workflow updates, and refreshed README/contributing docs.

Documentation

• Sphinx API reference added under docs/source/api/: generated RST for all instruments (BINOSPEC, DEIMOS, F2, FOURSTAR, GMOS, IMACS, LRIS, MMIRS, MOSFIRE, base instrument), primitives (absphot, calibration, image_procs, photometry, solve_wcs, sort_files), scripts (download_anet_index, download_gemini_data, download_keck_data, main_pipeline), and utils (logger, options, utilities).
• Installation and index (docs/source/installation.rst, docs/source/index.rst) updated with testing instructions (unit vs integration), links to README/CONTRIBUTING, and deployment note.
• docs/DEPLOY.md added with steps to enable GitHub Pages and deploy docs to https://ciera-transients.github.io/POTPyRI/.
• README updated: testing (unit vs integration, CI behavior), documentation section (online + local + deploy), and contributing (dev branch).
• CONTRIBUTING.md updated: branching from dev, offline test command, and PR target branches.

Testing

• Integration markers: Five tests that download fixtures from Google Drive are now @pytest.mark.integration (e.g. test_absphot, test_cal, test_photometry, test_sort, test_wcs_integration). Run pytest tests -m "not integration" for unit-only (no network).
• New unit tests:
  • tests/test_instruments.py — instrument_getter (unsupported instrument), Instrument base and GMOS: match_type_keywords, needs_sky_subtraction, getters (pixscale, rdnoise, gain, target, filter, exptime, ampl, binning, out_size, time, number, instrument_name, catalog), format_datasec, raw_format, naming helpers (stk/sci/bkg, mbias/mdark/mflat/msky).
  • tests/test_options.py — init_options, add_paths (raises when path missing, creates dirs).
  • tests/test_utilities.py — find_catalog (PS1, 2MASS, SDSS, UKIRT, SkyMapper, unsupported filter), is_number, parse_coord (degrees, sexagesimal, invalid).
  • tests/test_image_procs.py — test_create_error for image_procs.create_error.
• Bug fix: potpyri.utils.utilities.find_catalog early returns now consistently return a 6-tuple (catalog, catalog_ID, ra, dec, mag, err) to match the docstring and final return.

CI and workflows

• Build and Test (.github/workflows/build-test.yml): runs pytest -m "not integration" so CI does not depend on external fixture downloads.
• Documentation (.github/workflows/documentation.yml): deploy step runs only on push to main (not on pull_request), so PRs still build docs without updating the live site.

Environment and packaging

• Conda env name standardized to potpyri in environment.yml and related docs (replacing potpyri_test).
• pyproject.toml and package metadata/scripts remain aligned with current layout.

Scope

• ~80 files changed; substantial additions in potpyri/ (instruments, primitives, utils), tests/, and docs/.
• No intended change to the documented user workflow: main_pipeline INSTRUMENT DATA_PATH and options are unchanged.
• Unit test count (excluding integration): 60. All pass with pytest tests -m "not integration".

Checklist

• Unit tests pass: pytest tests -m "not integration"
• Docs build locally: cd docs && make html
• README and CONTRIBUTING reflect current setup