…polarGrid' into bp/offline-ACCESS-OM2

* origin/bp-claude/distributed-FPivot-TripolarGrid: (40 commits)
  Fix implicit MPI import in OrthogonalSphericalShellGrids
  Minimize test_mpi_tripolar.jl diff: rename vars, add diagnostic printing
  Fix formatting of reference list in index.md (CliMA#5397)
  Fix stale UZBC import in OrthogonalSphericalShellGrids
  Remove tmp_MPI_Gadi/ dev workspace and stray test output files
  Code review fixes: remove hardcoded Float64, expand index-tracing docs
  FC/FF col 1 fix: conjugate MPI exchange for non-fixed-point ranks (Rx > 2)
  Wider north buffer optimization: eliminate conjugate MPI, skip x-halo re-exchange for CC/CF
  Add new paper reference to Oceananigans documentation (CliMA#5395)
  Fix parallel test script: source defaults.sh, use --project=.
  Explicit imports in Grids (CliMA#5391)
  Load XESFM after Oceananigans (CliMA#5393)
  Fix rm ENOENT in simulation testsets: use force=true for NFS cleanup
  GPU isbits fix: make Tripolar.fold_topology a type parameter, consolidate tests
  Clean up distributed fold: GPU-safe views, batched MPI, DRY fold-line helpers
  Rewrite distributed fold pipeline: 4-step switch_north_halos! for Rx > 2
  Fix nranks guard: use exact equality instead of >= for partition tests
  Add Partition(4,2) index tracing test to diagnose fold corner bug
  Update simulation_debug for large-pencil 4×2 debugging
  Fix FPivot south masking and increase grid sizes for simulation tests
  ...