Unable to write out W2H fields with XIOS

Nobody has claimed this yet.

### Version

main

### Are there any linked Issues or Pull Requests?

#77

### What happened?

For a long time (possibly ever) it has not been possible to consistently write out W2H fields. This may depend on compiler / machine, and application (for instance it seems possible to write out fields in `gungho_model` but not `lfric_atm`).

This is important for writing out wind fields, as the workaround is to average the wind fields to the W3 function space, which can remove import grid-scale artifacts from the output.

The solution is likely to be in LFRic-Core, but is impacting LFRic-Apps.

### Relevant log output

```shell
Backtrace for this error:
terminate called after throwing an instance of 'xios::CException'

Program received signal SIGABRT: Process abort signal.

#1 0x14c207251d2b in ???
#2 0x14c2072533e4 in ???
#3 0x14c2104a5608 in _ZN9__gnu_cxx27__verbose_terminate_handlerEv
at ../../../../cpe-gcc-12.1.0-202208101649.1dfb26392197c/libstdc++-v3/libsupc++/vterminate.cc:95
#3 0x152a0a6a5608 in _ZN9__gnu_cxx27__verbose_terminate_handlerEv
at ../../../../cpe-gcc-12.1.0-202208101649.1dfb26392197c/libstdc++-v3/libsupc++/vterminate.cc:95
#4 0x152a0a6b0c89 in _ZN10__cxxabiv111__terminateEPFvvE
at ../../../../cpe-gcc-12.1.0-202208101649.1dfb26392197c/libstdc++-v3/libsupc++/eh_terminate.cc:48
#5 0x152a0a6b0cf4 in _ZSt9terminatev
at ../../../../cpe-gcc-12.1.0-202208101649.1dfb26392197c/libstdc++-v3/libsupc++/eh_terminate.cc:58
#6 0x152a0a6b0f46 in __cxa_throw
at ../../../../cpe-gcc-12.1.0-202208101649.1dfb26392197c/libstdc++-v3/libsupc++/eh_throw.cc:98
#7 0x41b4fc in _ZN4xios6CField18solveGridReferenceEv
at /tmp/spackadmin/tmp.11pYYoa69N.2025-08-28/spack-stage/spack-stage-xios-2701-lcybbxh4mmgiuroe2kvojdcdtelxuipf/spack-src/src/node/field.cpp:1604
#8 0x1b37c21 in _ZN4xios6CField30solveOnlyReferenceEnabledFieldEb
#9 0x1b49986 in _ZN4xios5CFile27solveOnlyRefOfEnabledFieldsEb
at /tmp/spackadmin/tmp.11pYYoa69N.2025-08-28/spack-stage/spack-stage-xios-2701-lcybbxh4mmgiuroe2kvojdcdtelxuipf/spack-src/src/node/file.cpp:839
#10 0x1ac7583 in _ZN4xios8CContext27solveOnlyRefOfEnabledFieldsEb
at /tmp/spackadmin/tmp.11pYYoa69N.2025-08-28/spack-stage/spack-stage-xios-2701-lcybbxh4mmgiuroe2kvojdcdtelxuipf/spack-src/src/node/context.cpp:870
#11 0x1acea86 in _ZN4xios8CContext14postProcessingEv
at /tmp/spackadmin/tmp.11pYYoa69N.2025-08-28/spack-stage/spack-stage-xios-2701-lcybbxh4mmgiuroe2kvojdcdtelxuipf/spack-src/src/node/context.cpp:1654
#12 0x1ad4a63 in _ZN4xios8CContext30postProcessingGlobalAttributesEv
at /tmp/spackadmin/tmp.11pYYoa69N.2025-08-28/spack-stage/spack-stage-xios-2701-lcybbxh4mmgiuroe2kvojdcdtelxuipf/spack-src/src/node/context.cpp:639
#13 0x1ad4f3e in _ZN4xios8CContext15closeDefinitionEv
#14 0x1c62c92 in cxios_context_close_definition
at /tmp/spackadmin/tmp.11pYYoa69N.2025-08-28/spack-stage/spack-stage-xios-2701-lcybbxh4mmgiuroe2kvojdcdtelxuipf/spack-src/src/interface/c/icdata.cpp:124
#15 0x4aceba in __lfric_xios_context_mod_MOD_initialise_xios_context
at /var/tmp/pbs.4673331.ehz100/vn2.2_orog_project/run25/lfric_atm/gnu_fast-debug-64bit-rbl32/lfric_xios_context_mod.f90:140
#16 0x47345b in init_xios_io_context
at /var/tmp/pbs.4673331.ehz100/vn2.2_orog_project/run25/lfric_atm/gnu_fast-debug-64bit-rbl32/driver_io_mod.F90:243
#17 0x4736e9 in __driver_io_mod_MOD_init_io
at /var/tmp/pbs.4673331.ehz100/vn2.2_orog_project/run25/lfric_atm/gnu_fast-debug-64bit-rbl32/driver_io_mod.F90:106
#18 0x45c947 in __gungho_model_mod_MOD_initialise_infrastructure
at driver/gungho_model_mod.F90:782
#19 0x450ab4 in __gungho_driver_mod_MOD_initialise
at driver/gungho_driver_mod.F90:154
#20 0x44b69d in lfric_atm
#21 0x44b7b0 in main
at /var/tmp/pbs.4673331.ehz100/vn2.2_orog_project/run25/lfric_atm/gnu_fast-debug-64bit-rbl32/lfric_atm.f90:19
```

Start with the linked issue #77 and the XIOS failure at src/node/field.cpp:1604, then trace the LFRic call from lfric_xios_context_mod.f90:140 through driver_io_mod.F90:243. Reproduce the behavior in gungho_model and lfric_atm, and treat the issue as done when W2H wind fields can be written consistently without the XIOS abort.

Written by the indexing model from the issue text.