fix: pin NequIP to legacy API

[njzjz-bot]

Fixes the CUDA test collection failure:

ImportError: cannot import name 'model_from_config' from 'nequip.model'

deepmd_gnn.nequip still uses the pre-0.7 NequIP API (nequip.model.model_from_config). NequIP 0.7+ removed that symbol, while the CI dependency setup already pins/overrides e3nn==0.4.4, which is compatible with NequIP 0.6.x. This PR pins NequIP to <0.7 consistently in runtime metadata, nox, and the CUDA workflow.

Verification:

• git diff --check
• python3 -m py_compile noxfile.py
• uv pip install --dry-run --overrides requirements-overrides.txt ... "nequip<0.7" "e3nn==0.4.4" ... --torch-backend auto resolves nequip==0.6.2

Authored by OpenClaw (model: custom-chat-jinzhezeng-group/gpt-5.5)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.06%. Comparing base (4d6071a) to head (4fe334e).

Additional details and impacted files

@@                  Coverage Diff                   @@
##           pt-expt-dense-edge-op     #125   +/-   ##
======================================================
  Coverage                  82.06%   82.06%           
======================================================
  Files                         12       12           
  Lines                       1299     1299           
======================================================
  Hits                        1066     1066           
  Misses                       233      233           

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