orbit/coords: pin the 3D variational dxdv driver's host-side coords to numpy

[jobovy]

What

Burndown PR-7. integrateFullOrbit_dxdv (the 3D variational/STM driver) builds a pure-numpy base state and converts it via coords.cyl_to_rect/rect_to_cyl/rect_to_cyl_vec around the C integrator. Each does xp = get_namespace(...), which under the forced all-backend harness returns torch even for the numpy data → torch.cos(numpy_array) raises. This is host-side numpy bookkeeping, not a backend/autodiff path (the planar twin already uses literal numpy.cos/sin).

• Add an inert xp=None keyword to coords.cyl_to_rect/rect_to_cyl/rect_to_cyl_vec (forwarded to get_namespace, which already takes an explicit xp= override; rect_to_cyl_vec forwards to its internal rect_to_cyl).
• Pass xp=numpy at the 3 dxdv-driver call sites in integrateFullOrbit.py.

Impact

Flips 37/41 test_liouville_3d_2d_bridge torch entries (the dop853_c C path). The remaining 4 + test_liouville_3d/test_dxdv_3d_c_vs_python need the central scalar-coercion (#987) for their pure-Python _EOM_dxdv force eval (and one test-side coords call) — they flip once #987 lands.

Byte-identity + review

The xp=None default is inert for every existing caller, so numpy AND data-first jax/torch dispatch are unchanged. Verified byte-identical: coords + dxdv-driver output hashes identical parent vs branch; test_coords.py 97/97 and the orbit liouville/dxdv slice 288/3 identical. Adversarially reviewed (4 angles, all refuted) — including a full audit of every caller of these widely-used coords functions (no positional-arg collisions with the keyword-only boundary), the load-bearing-and-complete numpy-pin, and no decorator interaction.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.93%. Comparing base (69659c6) to head (9bf3ee6).

Additional details and impacted files

@@              Coverage Diff               @@
##           feat/backends     #988   +/-   ##
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  Coverage          99.93%   99.93%           
==============================================
  Files                254      254           
  Lines              39820    39820           
  Branches             837      839    +2     
==============================================
  Hits               39795    39795           
  Misses                25       25           

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[github-actions]

All-backend test status (jax / torch)

Commit b4df5c81e8c887981413673ed2ec5f4d00ca45be

Green is achieved via the checked-in xfail-ledger (tests/backend_xfail.txt, applied xfail(strict=False)), so the metric to watch is the shrinking xfail count (burndown), not a raw pass count. A FAIL/ERR is an un-ledgered regression (reds the run). Because the ledger is non-strict, a now-passing ledgered test is a plain pass here (no per-push XPASS); burndown candidates -- in both directions -- are surfaced by the scheduled regen run, which rewrites the ledger from real outcomes. deferred is a separate burndown: tests skipped because they are unrunnable under the backend until the port is vectorized (see tests/backend_slow_skip.txt), e.g. the jax spherical-DF sampling/quadrature tests pending the Track F DF migration.

Overall: jax: 1057 passed · 265 xfail · 725 deferred | torch: 833 passed · 1210 xfail · 1 deferred

Ledger size: 2357 entries (jax=284, torch=2073).

Test shard	jax	torch
actionAngle	✅ 112 pass · 89 xfail	✅ 26 pass · 175 xfail
sphericaldf	✅ 164 pass · 26 xfail · 28 deferred	✅ 8 pass · 210 xfail
conversion + util + misc	✅ 86 pass · 5 xfail · 1 deferred	✅ 41 pass · 51 xfail
potential + scf + multipole	— (no result)	— (no result)
quantity + coords	✅ 287 pass · 49 xfail	✅ 189 pass · 147 xfail
orbit (energy/Jacobi + from_name)	✅ 0 pass · 0 xfail · 115 deferred	✅ 63 pass · 52 xfail
orbit + orbits (main)	✅ 0 pass · 0 xfail · 578 deferred	✅ 248 pass · 327 xfail
evolveddiskdf	✅ 35 pass · 0 xfail	✅ 32 pass · 3 xfail
jeans + dynamfric	✅ 17 pass · 2 xfail · 2 deferred	✅ 7 pass · 13 xfail · 1 deferred
qdf + pv2qdf + streamgapdf_impulse + noninertial	✅ 57 pass · 75 xfail · 1 deferred	✅ 14 pass · 119 xfail
streamgapdf	✅ 28 pass · 2 xfail	✅ 27 pass · 3 xfail
diskdf	✅ 129 pass · 0 xfail	✅ 112 pass · 17 xfail
streamdf + streamspraydf + streamTrack	✅ 142 pass · 17 xfail	✅ 66 pass · 93 xfail

Per-shard counts

Test shard	backend	pass	xfail	deferred	XPASS	fail	error
actionAngle	jax	112	89	0	0	0	0
actionAngle	torch	26	175	0	0	0	0
sphericaldf	jax	164	26	28	0	0	0
sphericaldf	torch	8	210	0	0	0	0
conversion + util + misc	jax	86	5	1	0	0	0
conversion + util + misc	torch	41	51	0	0	0	0
potential + scf + multipole	jax	—	—	—	—	—	—
potential + scf + multipole	torch	—	—	—	—	—	—
quantity + coords	jax	287	49	0	0	0	0
quantity + coords	torch	189	147	0	0	0	0
orbit (energy/Jacobi + from_name)	jax	0	0	115	0	0	0
orbit (energy/Jacobi + from_name)	torch	63	52	0	0	0	0
orbit + orbits (main)	jax	0	0	578	0	0	0
orbit + orbits (main)	torch	248	327	0	0	0	0
evolveddiskdf	jax	35	0	0	0	0	0
evolveddiskdf	torch	32	3	0	0	0	0
jeans + dynamfric	jax	17	2	2	0	0	0
jeans + dynamfric	torch	7	13	1	0	0	0
qdf + pv2qdf + streamgapdf_impulse + noninertial	jax	57	75	1	0	0	0
qdf + pv2qdf + streamgapdf_impulse + noninertial	torch	14	119	0	0	0	0
streamgapdf	jax	28	2	0	0	0	0
streamgapdf	torch	27	3	0	0	0	0
diskdf	jax	129	0	0	0	0	0
diskdf	torch	112	17	0	0	0	0
streamdf + streamspraydf + streamTrack	jax	142	17	0	0	0	0
streamdf + streamspraydf + streamTrack	torch	66	93	0	0	0	0