Add rigid subcommand for rigid-only alignment

[tctco]

Motivation

• Provide a simple subcommand that performs rigid-only alignment by updating the image affine without performing resampling, intensity scaling, or nonlinear warping.
• Allow callers to opt into a lightweight flow useful for cases that only need affine correction (simpler than adni-pet-core).

Description

• Added a new spatial normalization CLI module rigid with localizer/src/spatialNormalizations/rigid/RigidCLI.h and .../RigidCLI.cpp that accepts base arguments and triggers a rigid-only request.
• Introduced a rigidOnly flag in localizer/src/core/common/NormalizationContracts.h to represent the rigid-only mode in the normalization options.
• Updated localizer/src/core/services/SpatialNormalizationService.cpp to return the rigid-aligned image as the final output when rigidOnly is set and to skip ADNI-style postprocessing in that case.
• Registered the new module in localizer/src/spatialNormalizations/ModuleCatalog.cpp and added the new source files to localizer/src/CMakeLists.txt; also added a quick CLI test case in localizer/src/tests/test_quick_cli.py for rigid --help.

Testing

• Ran the quick CLI help test case with pytest -q localizer/src/tests/test_quick_cli.py -k rigid_help, which errored because the test environment expected the DCCCcore executable at localizer/src/install/bin/DCCCcore and it was not present, so the test could not complete.

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Codex Task