Fix Python 3.14 CI mypy breakage in masked-array call sites

[Copilot]

The build (ubuntu-latest, 3.14) job was failing in the pre-commit mypy step due to Python 3.14 typing incompatibilities around numpy.ma.masked_array(...) call sites. This PR updates the affected masked-array usage patterns to keep behavior unchanged while restoring type-check compatibility.

• Type-check compatibility updates (production code)

  • Replaced ma.masked_array(...) with ma.array(...) at impacted call sites where mypy reported "TypeAliasType" not callable.
  • Updated masked comparison logic in clutter detection to use numpy.ma operations so .filled(...) remains valid for masked results.

• Type-check compatibility updates (tests)

  • Applied the same ma.masked_array(...) → ma.array(...) adjustment in impacted tests to keep test fixtures aligned with typed usage.

• Representative change

  # before
  array = ma.masked_array(array)
  
  # after
  array = ma.array(array)

  # before
  tiny_velocity = (np.abs(v[:, :n_gates]) < v_lim).filled(False)
  
  # after
  tiny_velocity = ma.less(ma.abs(v[:, :n_gates]), v_lim).filled(False)