Add coverage for compatibility output parsing paths

[Copilot]

This adds targeted regression coverage for the compatibility-output path introduced on this branch. The new tests exercise parsed fixture data directly instead of only checking that expected keys exist.

• What changed

  • Added assertions for compatibility_output fixture parsing in tests/test_compatibility_file.py
  • Verified representative parsed values for:
    • MD timesteps / atom counts
    • thermo output
    • first-frame positions / velocities
    • pressure tensor mapping
  • Added coverage for the calc_dataclass type guard by asserting invalid dataclass input raises TypeError
  • Added coverage for input_control_file entries that do not replace existing commands, ensuring they are appended to lmp.in

• Why this matters

  • Tightens coverage around the new compatibility-output behavior so regressions are caught at the interface level
  • Ensures both parsed data content and input-file generation behavior are validated, not just presence of output keys

• Example

  np.testing.assert_array_equal(
      parsed_output["generic"]["steps"], np.arange(0, 1100, 100)
  )
  np.testing.assert_allclose(
      parsed_output["generic"]["pressures"][0], expected_first_pressure
  )
  self.assertIn("neighbor 0.3 bin\n", content)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.22%. Comparing base (1416ace) to head (c02fb9d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
+ Coverage   89.05%   89.22%   +0.16%     
==========================================
  Files          12       12              
  Lines        1197     1197              
==========================================
+ Hits         1066     1068       +2     
+ Misses        131      129       -2     

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