DLESyM checkpoint compat fixes

[pzharrington]

PhysicsNeMo Pull Request

Description

#1827 actually broke the previous dlesym checkpoints (dlesym-v1-era5-v1.0 and dlesym-v0-isccp-era5). These fixes add some backward compat shims to checkpoint load so older checkpoints of previous dlesym variants will still run.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• The CHANGELOG.md is up to date with these changes.
• An issue is linked to this pull request.
• If I am implementing a new model or modifying any existing model, I have followed the Models Implementation Coding Standards.

Dependencies

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CODEOWNERS review map

Current for commit 61e1fe1caa96. An approval covers every file listed for that owner; one owner is sufficient for shared files.

⏳ @pzharrington — 4 file(s)

• physicsnemo/models/dlwp_healpix/HEALPixRecUNet.py
• physicsnemo/models/dlwp_healpix/HEALPixUNet.py
• physicsnemo/models/dlwp_healpix/layers/init.py
• physicsnemo/models/dlwp_healpix/layers/healpix_blocks.py

Comment /codeowners-info to refresh.

[greptile-apps]

Greptile Summary

The PR restores compatibility with older DLESyM checkpoints by versioning both HEALPix U-Net variants, rewriting legacy constructor configurations, preserving the historical residual-skip rule, and backfilling a duplicated activation buffer during state loading.

• Advances the HEALPix model checkpoint version to 0.3.0 and maps versions 0.1.0 and 0.2.0 forward.
• Detects pre-v1.1 constructor arguments and restores legacy skip and diagnostic behavior.
• Adds a block-level compatibility flag and tolerant loading for legacy activation-cap state keys.

Important Files Changed

Filename	Overview
physicsnemo/models/dlwp_healpix/HEALPixRecUNet.py	Advances checkpoint versioning and applies the shared legacy argument mapper for recurrent HEALPix checkpoints.
physicsnemo/models/dlwp_healpix/HEALPixUNet.py	Advances checkpoint versioning and applies the shared legacy argument mapper for non-recurrent HEALPix checkpoints.
physicsnemo/models/dlwp_healpix/layers/init.py	Adds structurally gated legacy argument rewriting; behavior is consistent with historical construction, but two new helper docstrings violate repository formatting requirements.
physicsnemo/models/dlwp_healpix/layers/healpix_blocks.py	Adds the selectable historical skip rule and activation-cap state backfill; the compatibility behavior is coherent, with one new docstring using the wrong string prefix.

_{Reviews (1): Last reviewed commit: "dlesym checkpoint compat" | Re-trigger Greptile}

[pzharrington]

/ok to test 61e1fe1