feat: COOLEST standard interop — profile converters + template import/export

[Jammy2211]

Overview

Preparation for modeling ~18,000 Euclid DR1 lenses: PyAutoLens results must be exchangeable with lenstronomy/herculens/Glee via the COOLEST standard (https://github.com/aymgal/COOLEST). This task adds a conversion layer at the model I/O boundary covering all profiles COOLEST defines — internals unchanged (sampling stays on (e1,e2); no internal convention flip), per the Slack consensus (Sonnenfeld, Galan). The intermediate-axis question is handled by a follow-up PowerLawIntermediate + herculens-parity task (PyAutoMind/draft/feature/autolens/coolest_powerlaw_herculens_parity.md).

Plan

• PyAutoGalaxy: new autogalaxy/interop/coolest/ package — pure, dependency-free bidirectional parameter converters for every COOLEST-defined light/mass profile (ellipticity, angle, intermediate-axis radius conventions), reusing autogalaxy/convert.py.
• PyAutoLens: new autolens/interop/coolest.py — COOLEST JSON template import/export of full lens models (analytic profile parameters only) via the coolest pip package as an optional dependency.
• Explicit, documented Einstein-radius definition on export (COOLEST intermediate-axis profile parameter; distinguished from the DR1 tangential-critical-curve definition).
• Round-trip + numerical-certification tests for every √q / angle factor in both repos.
• Workspace guide + workspace_test script as a follow-up PR behind the library-first merge gate.

Detailed implementation plan

Affected Repositories

• PyAutoLens (primary)
• PyAutoGalaxy

Branch Survey

Repository	Current Branch	Dirty?
./PyAutoGalaxy	main	clean
./PyAutoLens	main	paper_jax/paper.md modified (pre-existing, unrelated)

Suggested branch: feature/coolest-standard-support
Work classification: Library (workspace follow-up)
Worktree root: ~/Code/PyAutoLabs-wt/coolest-standard-support/

Convention facts (verified against coolest.readthedocs.io)

Quantity	COOLEST	PyAutoGalaxy/PyAutoLens
Coordinates	cartesian (x right, y up), arcsec	(y, x) grids, arcsec
Position angle	CCW from +y (East-of-North), (-90°, +90°]	CCW from +x, (-45°, 135°] (autogalaxy/convert.py) → φ_coolest = angle_ag − 90° renormalized
Ellipticity	q = b/a + PA	(e1, e2) ell_comps — ell_comps_from / axis_ratio_and_angle_from
Radii (r_eff, θ_E)	intermediate axis r = √(a·b) = √q·a	profile-specific; PowerLaw uses the 2/(q^-½+q^½) rescale (profiles/mass/total/power_law.py) — per-profile factors derived and numerically certified
Shear	γ_ext, φ_ext	(gamma_1, gamma_2) — shear_magnitude_and_angle_from
Template I/O	coolest pip package (coolest.template)	new optional dependency in PyAutoLens

Implementation Steps

Phase A — PyAutoGalaxy autogalaxy/interop/coolest/

1. conventions.py — angle (+x ↔ East-of-North), (e1,e2) ↔ (q, PA), (y,x) ↔ (x,y) centre swap, per-profile radius-factor helpers. Reuse autogalaxy/convert.py; do not duplicate its math.
2. light.py — ag.lp.Sersic ↔ COOLEST Sersic (effective-radius factor audited against ag's elliptical-radius definition); shapelets if supported by the installed coolest version.
3. mass.py — ag.mp.Isothermal ↔ SIE, ag.mp.PowerLaw ↔ PEMD/EPL (θ_E intermediate-axis conversion), ag.mp.NFW ↔ NFW, ag.mp.ExternalShear ↔ ExternalShear, ag.mp.MassSheet ↔ convergence sheet if defined.
4. Converters are dict-in/dict-out on plain floats (no coolest import in autogalaxy — zero new dependencies). Unsupported profiles raise a clear, named error (no silent skips).
5. Tests test_autogalaxy/interop/ (numpy-only): per-profile round-trip identity + numerical certification — evaluate the ag profile and the profile reconstructed from its COOLEST parameters, assert equal convergence/deflections; for PowerLaw assert the analytic √q relation between θ_E definitions.

Phase B — PyAutoLens autolens/interop/coolest.py
6. to_coolest(galaxies_or_tracer, file_path) — export analytic profile parameters into a COOLEST JSON template (lensing entities from lens/source galaxies, redshifts from Galaxy.redshift), via the Phase A registry. Lazy coolest import with informative error; pip install autolens[coolest] extra; added to test/dev extras so CI exercises it.
7. from_coolest(file_path) -> Tracer — read a template, build ag/al profiles via the inverse mappings (built to consume Sonnenfeld's golden-lens JSONs).
8. Einstein-radius definition documented in module docstring + template metadata.
9. Tests test_autolens/interop/: full-model round-trip (PowerLaw + Shear lens, Sersic light + Sersic source), template written and re-read with coolest.template, parameters equal to input; end-to-end convergence/deflection equality on a grid.

Phase C — workspace follow-up PR (after library merge)
10. Minimal autolens_workspace/scripts/guides/ COOLEST example + autolens_workspace_test round-trip script.

Key Files

• PyAutoGalaxy/autogalaxy/convert.py — existing (e1,e2)/(q,PA)/shear converters to reuse
• PyAutoGalaxy/autogalaxy/profiles/mass/total/power_law.py — the 2/(q^-½+q^½) Einstein-radius rescale to map
• PyAutoGalaxy/autogalaxy/interop/coolest/{conventions,light,mass}.py — new
• PyAutoLens/autolens/interop/coolest.py — new
• test_autogalaxy/interop/, test_autolens/interop/ — new tests

Original Prompt

Click to expand starting prompt

See PyAutoMind/active/coolest_standard_support.md (filed from the COOLEST Slack thread with Alessandro Sonnenfeld and Aymeric Galan; original request verbatim inside).

[Jammy2211]

Library PRs Created

• PyAutoGalaxy: feat: COOLEST-standard profile parameter converters (autogalaxy.interop.coolest) PyAutoGalaxy#501 — autogalaxy.interop.coolest parameter converters (dependency-free, dict-in/dict-out; Sersic/SIE/PEMD/NFW/shear/sheet; sqrt(q) and angle conventions derived + numerically certified). 982 tests passed.
• PyAutoLens: feat: COOLEST template import/export (autolens.interop.coolest) #613 — autolens.interop.coolest.to_coolest / from_coolest COOLEST JSON template I/O (coolest optional extra; NFW sigma_crit from cosmology; Einstein-radius definition documented). 385 tests passed. Merge the PyAutoGalaxy PR first.

Heart was RED on 6 pre-existing, unrelated reasons at ship time; shipped through on explicit user acknowledgement (commit/push/PR-open only).

API changes: Added only (new ag.interop / al.interop namespaces + coolest extra) — no workspace script is affected (grep confirms no interop usage).

Next:

1. Merge both PRs (library-first), then a minimal autolens_workspace COOLEST guide + autolens_workspace_test round-trip script as a follow-up PR (Phase C).
2. Follow-up task (filed, starts after this merges): PowerLawIntermediate profile + herculens EPL cross-code parity via a shared COOLEST file — PyAutoMind/draft/feature/autolens/coolest_powerlaw_herculens_parity.md.