Add DIR_TRANS API tests

[samhatfield]

Adds the following API tests for DIR_TRANS:

• ectrans_test_trans_api_dir_trans_call_mode_1_scalar_1
• ectrans_test_trans_api_dir_trans_call_mode_1_wind_1
• ectrans_test_trans_api_dir_trans_call_mode_1_wind_1_scalar_1
• ectrans_test_trans_api_dir_trans_call_mode_2_pgp3a_1
• ectrans_test_trans_api_dir_trans_call_mode_2_pgp3b_1
• ectrans_test_trans_api_dir_trans_call_mode_2_wind_1

[Copilot]

Pull request overview

Adds a new API test suite covering the DIR_TRANS entry point across multiple call modes/configurations, and wires it into the existing API-test CMake infrastructure.

Changes:

• Introduces DIR_TRANS API tests (scalar, wind, mixed; call modes 1 and 2) in a new Fortran test suite module.
• Adds a dir_trans API test CMake target list and registers it with the top-level tests/trans/api CMake.
• Expands the API test matrix to run these tests across configured MPIxOMP combinations and backends.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
tests/trans/api/dir_trans/dir_trans_test_suite.F90	New Fortran API tests validating basic DIR_TRANS behavior for scalar and wind fields.
tests/trans/api/dir_trans/CMakeLists.txt	New CMake definition to generate/register the DIR_TRANS API test suite across backends and MPI/OMP configs.
tests/trans/api/CMakeLists.txt	Adds the dir_trans subdirectory so the new suite is built and executed.

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