Better chunking strategies for constlat intersections and zonal routines. - #1624

…rite intersections, add 241 baseline testsgit status! - most came from accusphere

…tion docstring

…us/mask, dispatcher

…r_sq<0

- benchmarks/geometry_kernels.py: ASV micro-benchmarks for all three
  layers of the EFT intersection stack (_accux_gca, _try_gca_gca_intersection,
  gca_gca_intersection, _accux_constlat, _try_gca_const_lat_intersection,
  gca_const_lat_intersection) plus EFT primitives and point-in-polygon;
  all functions warmed before timing so results reflect steady-state cost
- test/test_plot.py: add test_to_raster_auto_extent verifying that the
  axis limits change and the raster contains finite data

…rectness fixes

Review comments addressed:
- Remove "near-double precision" / "sufficient" overclaims; say "roughly twice
  as accurate" and note the robustness tier boundary clearly
- Explain _lon_bounds_from_vertices is required for UXarray antimeridian
  encoding and cannot be removed
- Add block comment before _no_extreme functions clarifying they are
  pre-existing edge screeners unrelated to the EFT stack
- Document SoS as explicit future work in _point_in_polygon_sphere docstring
- L2 pos_fin/neg_fin: replace ternary with int(); exploit neg=-pos symmetry
- Label computation: drop dead local*0 term, use integer mask arithmetic
- Remove vertex-lat snap from bounds: _face_location_info already captures
  interior arc extrema accurately via the compensated kernel
- _ON_MINOR_ARC_TOL: document intentional 1e-10 vs C++ 1e-8 divergence

Bug fixes:
- on_minor_arc: add antipodal-endpoint guard; a x b = 0 for antipodal inputs
  so every point on the great circle passes the collinearity test (false pos)
- bounds.py: replace mask arithmetic use_ext*z_ext + (1-use_ext)*z_edge with
  plain if/else; 0*NaN = NaN propagates when norm=0, if/else does not
- _point_in_polygon_sphere: ray-nudge now restarts the loop from i=0 so all
  edges are counted with the same ray (mid-loop nudge corrupted crossing parity)

Cleanup:
- Remove _flip_sign, _SIGN_NEG, _SIGN_POS, _SIGN_ZERO dead code from
  point_in_face.py; inline literals in _counts_as_crossing
- Remove _SNAP_TOL_DEG constant and snap_tol_deg parameter throughout bounds.py
- Notebook: fix Grid.get_point_on_face -> get_faces_containing_point; remove
  incorrect geometry.py row from Section 4 table; add accucross_pair and
  acc_sqrt_re to Section 2 building-blocks table

…PI name

- ci/environment.yml: pin tornado<6.5.7 to avoid ssl.SSLError in panel 1.9.3
  on Python 3.11 Windows (conda-forge regression, 2026-06-10)
- intersections.py: remove _gca_gca_intersection_cartesian shim (dead code);
  add comment explaining _snap_const_lat_endpoint snap_sq constant
- test_intersections.py: update 4 call sites to use gca_gca_intersection directly
- spherical-geometry-accuracy.ipynb: fix stale Grid.get_point_on_face ->
  Grid.get_faces_containing_point (2 occurrences)

Closes #1509

…rite intersections, add 241 baseline testsgit status! - most came from accusphere

…tion docstring

…us/mask, dispatcher

…r_sq<0

Reconcile diverged accusphere branch. Resolutions:
- intersections.py: restore inline=always on L1 kernels (_accux_constlat,
  _accux_gca) for allocation scalar-replacement
- point_in_face.py: keep restart-loop ray casting (consistent parity),
  adopt named sign constants, drop unused _flip_sign
- arcs.py: keep antipodal-endpoint guard in on_minor_arc
- bounds.py: keep vertex-latitude snapping (snap_tol_deg) path
- computing.py: keep detailed docstring with SIAM/EGUsphere references

Add an LLVM fma intrinsic and route two_prod through a single fused
multiply-add for its error term on hardware that supports it, selected at
import time and validated to be bit-exact against the Veltkamp split. Falls
back to the portable Veltkamp form otherwise, so there is no hard FMA
dependency.

The FMA path is ~2x faster in the compensated geometry kernels (each
two_prod drops from ~17 flops to one FMADD) and is numerically identical:
all 241 AccuSphGeom baseline cases pass unchanged.

Add _accux_constlat_scalar, which takes the arc endpoints as six scalars and
returns the candidate coordinates as scalars instead of two np.empty(3)
arrays. _accux_constlat now wraps it so the array API is unchanged.

Returning scalars lets Numba keep the candidates in registers, so a batch
loop over many edges does no per-point heap allocation. On a 16M-point
const-lat sweep this is ~2.7x faster than the array-returning path and drops
the AccuX/FP64 cost ratio from ~19x to ~7x. Bit-identical results; all 241
AccuSphGeom baseline cases pass.