Save json namelist during serialization

[jcanton]

and bug-fix the run_serialization script with lazy loading

[Copilot]

Pull request overview

This PR updates the serialization workflow to also persist the ICON namelist as JSON during output collection, and adjusts the run_serialization CLI to use lazy imports and updated repository directory settings.

Changes:

• Add f90nml as a scripts dependency and lock it in uv.lock.
• Extend copy_ser_data() to convert NAMELIST_ICON_output_atm to JSON and save it alongside copied outputs.
• Refactor run_serialization.py settings (repo dir fields) and introduce lazy loading for icon4py.model.testing imports.

Reviewed changes

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

File	Description
uv.lock	Locks f90nml and updates the lock revision/markers.
scripts/python/run_serialization.py	Adds namelist-to-JSON conversion, lazy imports, and updates settings/path wiring.
pyproject.toml	Adds f90nml>=1.5 to the scripts dependency group.
model/testing/src/icon4py/model/testing/definitions.py	Adds NAMELIST_ICON_FNAME constant for the ICON output namelist filename.

Comments suppressed due to low confidence (1)

scripts/python/run_serialization.py:76

• SerializationSettings.defaults() now relies on the module-level definitions being initialized elsewhere (it was previously imported locally). This makes defaults() fragile if it’s ever called without first running the lazy-import bootstrap. Consider importing definitions (and any other required modules) inside defaults() again, or refactor so defaults() doesn’t depend on mutable module globals.

    def defaults(cls) -> SerializationSettings:
        # ======================================
        # START DEFAULT USER CONFIGURATION
        # ======================================
        # We hardcode the settings here for simplicity, but they could be
        # extended to be read from a config file or command-line arguments
        # if needed in the future.

        COMM_SIZES: list[int] = [1, 2, 4]

        EXPERIMENTS = [
            definitions.Experiments.MCH_CH_R04B09,
            definitions.Experiments.JW,
            definitions.Experiments.EXCLAIM_APE,
            definitions.Experiments.GAUSS3D,
            definitions.Experiments.WEISMAN_KLEMP_TORUS,
        ]

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[jcanton]

cscs-ci run default

[github-actions]

Mandatory Tests

Please make sure you run these tests via comment before you merge!

• cscs-ci run default
• cscs-ci run distributed

Optional Tests

To run benchmarks you can use:

• cscs-ci run benchmark-bencher

To run tests and benchmarks with the DaCe backend you can use:

• cscs-ci run dace

To run test levels ignored by the default test suite (mostly simple datatest for static fields computations) you can use:

• cscs-ci run extra

For more detailed information please look at CI in the EXCLAIM universe.

[jcanton]

cscs-ci run distributed