dbSta: check LEF and Liberty area consistency

[mahjiid]

Summary

Adds the unchecked LEF/LIB area-consistency validation from #4872 to check_ip.

Changes

• Compute each LEF macro's physical area from its database width/height and DBU scale.
• Compare it with the matching Liberty cell area.
• Allow a small 0.1% tolerance to avoid floating-point representation noise.
• Report an IP-check warning when the values disagree.
• Extend the existing LEF/Liberty regression fixture with an intentional 1.0 vs 2.0 area mismatch.

Validation

• git diff --check passes.
• Commit includes DCO sign-off.
• Regression is integrated into the existing check_ip_liberty_pins pass/fail test.
• A full local OpenROAD build was not run because the Windows host does not have the OpenROAD C++ build toolchain installed; CI should exercise the existing registered test.

Part of #4872

[gemini-code-assist]

Code Review

This pull request introduces a new check (LEF/LIB-CHK-013) to verify that cell areas match between LEF and Liberty files, implementing the comparison logic in IpChecker::checkLibertyPins and adding corresponding test cases. Feedback on the implementation highlights a potential division-by-zero vulnerability if dbu_per_micron is zero, suggesting a guard condition to make the code more robust.

[gemini-code-assist]

If dbu_per_micron is 0 (which can happen if the database units are not properly initialized or defined in the LEF), dividing by it will result in a division-by-zero error, producing inf or nan values. Adding a guard to ensure dbu_per_micron > 0 before performing the division is a safer and more robust approach.

    const double dbu_per_micron = tech->getDbUnitsPerMicron();
    if (dbu_per_micron > 0) {
      const double lef_area
          = static_cast<double>(master->getWidth()) * master->getHeight()
            / (dbu_per_micron * dbu_per_micron);
      const double liberty_area = liberty_cell->area();
      const double area_tolerance = std::max(1e-6, lef_area * 1e-3);

      if (std::abs(lef_area - liberty_area) > area_tolerance) {
        logger_->warn(utl::CHK,
                      122,
                      "Master {} area mismatch between LEF ({:.6f}) and "
                      "Liberty ({:.6f})",
                      master_name,
                      lef_area,
                      liberty_area);
        warning_count_++;
      }
    }