Migrate pure-Julia SOFA implementation from Astrometry.jl (v2.0) (#38)

## Summary

Replaces the `SOFA_jll`-based C wrapper on `main` with the **pure Julia
implementation of SOFA release 19 (2023-10-11)**, migrated from the
`Astrometry.SOFA` submodule of
[Astrometry.jl](https://github.com/JuliaAstro/Astrometry.jl) (at
`b5780028`), originally developed by Paul Barrett (@barrettp). This
begins the v2.0 line; the v1.x C-wrapper releases remain maintained on
their `release-1.x` branches.

## Commit structure

1. **`c189472` — pristine migration.** The implementation as it exists
in Astrometry.jl, copied with minimal adaptation. Reviewers can diff
this commit against upstream directly.
2. **`573a121` — case-collision fix.** `src/sofa.jl` →
`src/sofa_base.jl`: the original name collides with the `src/SOFA.jl`
entry point on case-insensitive filesystems (macOS/Windows), which broke
checkout/precompile on those CI runners.
3. **`6240bee` — layout refactor.** All moves are `git mv` renames, load
order unchanged:
- the 15 topical files move from the vestigial `src/SOFA/` nesting up to
`src/`
- the 11 `constants*.jl` files are collected into a new `src/constants/`
directory (filenames unchanged)
- `src/sofa_base.jl` → `src/base.jl`, with its include list moved into
`src/SOFA.jl` so the module file owns the file tree; `base.jl` now holds
only the shared types, leap-second table, and ephemeris helpers

## What moved

- ~23.5k lines: 15 topical implementation files, 11 `constants*.jl`
files, `util.jl`, `ephemerisDE405.jl`, and the shared types/leap-second
table — replacing all 245 C-wrapper files
- `test/sofatests.jl` — the SOFA validation suite (401 tests), replacing
the C-wrapper `test_sofa.jl`
- New top-level `module SOFA` (promoted from the nested Astrometry
submodule), same export surface

## Final layout

```
src/
  SOFA.jl          # module: docstring, exports, usings, full include list
  base.jl          # shared types, leap-second table, ephemeris helpers (was sofa_base.jl)
  util.jl
  ephemerisDE405.jl
  constants/       # the 11 constants*.jl files, names unchanged
  astrometry.jl, calendars.jl, … vectorops.jl   # 15 topical files
```

## Adaptations during the port

- Inlined `ephem_position`/`ephem_velocity` (from Astrometry's
`model2000.jl`) into `base.jl`, removing the only parent-module
dependency
- Fixed two upstream export typos caught by the export check: `po6e` →
`p06e`, `f2wxy` → `fw2xy`
- `Project.toml`: drop `SOFA_jll`/`Libdl`, add `LinearAlgebra` +
`StaticUnivariatePolynomials`; `version = "2.0.0-DEV"`; Paul Barrett
added to authors
- README/docs updated for the pure-Julia description, with SOFA-license
derived-work acknowledgment

## Breaking changes (v2.0)

- Routine names drop the `iau` prefix: `iauCal2jd` → `cal2jd`, etc.
- No binary dependency; results are computed in native Julia

## Validation

- `Pkg.test()` locally (Julia 1.12.6, linux): **401/401 pass**,
re-verified after each of the three commits
- `Aqua.test_all(SOFA, ambiguities=false)`: all checks pass (incl.
undefined exports, stale deps, compat bounds)
- `docs/make.jl`: builds clean (sofa.md page 626 KiB, under the
configured 800 KiB threshold)
- First CI push: linux/Aqua/Documentation green; macOS/Windows failed on
the case collision addressed by `573a121`
- Note: codecov/patch may stay noisy on a whole-package replacement; not
a correctness signal

## Follow-up

- Drop SOFA from Astrometry.jl

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: icweaver

Project.toml

@@ -1,18 +1,18 @@
 name = "SOFA"
 uuid = "ad3d3fd0-b5f2-51ee-b274-8cdbe62317e2"
-authors = ["Duncan Eddy <duncan.eddy@gmail.com>"]
-version = "1.1.1"
+authors = ["Duncan Eddy <duncan.eddy@gmail.com>", "Paul Barrett <pebarrett@gmail.com>"]
+version = "2.0.0"
 
 [workspace]
 projects = ["test", "docs"]
 
 [deps]
-Libdl = "8f399da3-3557-5675-b5ff-fb832c97cbdb"
-SOFA_jll = "d1004450-2f34-5761-9671-ec24e6a6fe03"
+LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
+StaticUnivariatePolynomials = "6f584044-cad5-5b68-a429-1e244a824f76"
 
 [compat]
-Libdl = "1"
-StaticArrays = "^1.0.1"
-SOFA_jll = "2019.7.22"
-julia = "1.10.0"
+LinearAlgebra = "1"
+StaticArrays = "1.9"
+StaticUnivariatePolynomials = "0.6"
+julia = "1.10"

README.md

@@ -8,14 +8,14 @@
 [![Aqua QA](https://raw.githubusercontent.com/JuliaTesting/Aqua.jl/master/badge.svg)](https://github.com/JuliaTesting/Aqua.jl)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
-Unofficial wrapper of the IAU SOFA C libraries for fundamental astronomy. See the [Astrometry.jl > SOFA](https://juliaastro.org/Astrometry/stable/SOFA/) sub-package for the pure Julia implementation.
+A pure Julia implementation of the IAU SOFA library for fundamental astronomy. For the wrapper of the SOFA C library, see the v1.x releases maintained on the `release-1.x` branches.
 
 ## Description
 
-The purpose of this package is to wrap the SOFA C library of fundamental astonomical function to make it easily accessible in Julia. This package serves as a _wrapper_ only. All functions ultimately call the original, unmodified, SOFA C library functions which are compiled as part of the package build process.
+This package provides a pure Julia implementation of the SOFA library of fundamental astronomical functions, originally developed by Paul Barrett as the `SOFA` submodule of [Astrometry.jl](https://github.com/JuliaAstro/Astrometry.jl). No compiled C library is required.
 
-The full SOFA C test suite is reproduced as part of the package to
-prove compliance and reproducibility of the core SOFA C functionality.
+The SOFA C test suite is reproduced as part of the package to
+prove compliance and reproducibility of the core SOFA functionality.
 
 ## Package Version <-> SOFA Release Correspondence
 
@@ -35,8 +35,12 @@ The planned package versions below correspond to the following releases of the S
 ## Notes
 
 1. All computed values are returned by the function call. No values are returned by reference.
-2. Wrappers for _iauAtciqn_, _iauAticqn_, and _iauLdn_ do not currently work properly.
+2. As of v2.0, function names follow the SOFA names without the `iau` prefix (e.g. `cal2jd` instead of `iauCal2jd`).
 
 ## Compliance with SOFA License
 
 This distribution is permitted and compliant with the SOFA license. See the LICENSE for details.
+
+This package is derived from, but is not an official product of, the International
+Astronomical Union SOFA collection (http://www.iausofa.org), and is not endorsed
+by the IAU SOFA Board.

docs/src/index.md

@@ -1,4 +1,4 @@
 # SOFA.jl Documentation
 
-This module provides a Julia wrapper for International Astronomical Union Standards
-of Fundamental Astronomy [SOFA](https://www.iausofa.org/) module.
+This module provides a pure Julia implementation of the International Astronomical
+Union Standards of Fundamental Astronomy [SOFA](https://www.iausofa.org/) library.