Add input validation for bias parameter in cylindrical basis

[Copilot]

The bias parameter in cylindrical basis configuration is parsed from YAML and multiplied into acyl during EmpCylSL construction, but lacked input validation. Invalid values (negative, zero, NaN, infinite) would propagate through to basis construction, causing unclear failures.

Changes

• Added validation after YAML parsing in BiorthBasis.cc to require bias > 0 and finite
• Validation placed in existing parameter enforcement section (lines 1561-1570) for consistency
• Error messages indicate the constraint violated and the invalid value received

// Validate bias parameter
//
if (!std::isfinite(bias)) {
  throw std::runtime_error("Cylindrical: 'bias' parameter must be finite");
}
if (bias <= 0.0) {
  std::ostringstream sout;
  sout << "Cylindrical: 'bias' parameter must be positive, got " << bias;
  throw std::runtime_error(sout.str());
}

Invalid configs now fail immediately with clear diagnostics rather than producing broken basis instances.

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