Add DCOPF

[klamike]

Not totally sure it makes sense to have it here. But it can be useful to have around for testing.

[Copilot]

Pull request overview

This PR adds DC Optimal Power Flow (DCOPF) functionality to ExaModelsPower, providing a linearized power flow formulation for testing purposes. The implementation follows the existing patterns in the codebase for polar and rectangular AC OPF formulations.

Key changes:

• Implements DCOPF model with voltage angle variables, active power generation, and active power flow
• Adds Ohm's law constraint for DC approximation using susceptance calculations
• Integrates comprehensive test suite comparing against PowerModels.jl DCPPowerModel results

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/dcopf.jl	New file implementing DCOPF formulation with build_dcopf and dcopf_model functions following the opf.jl pattern
src/constraint.jl	Adds c_ohms_law_dcopf constraint function implementing DC power flow equations
src/ExaModelsPower.jl	Reorders includes to ensure constraint.jl is loaded before dcopf.jl, enabling constraint function usage
test/opf_tests.jl	Adds test_dcopf_case function to validate DCOPF results against PowerModels reference solutions
test/runtests.jl	Adds DCOPF test suite covering multiple cases, backends, and precision levels

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.18%. Comparing base (1663aa0) to head (bc0abbd).
⚠️ Report is 1 commits behind head on ss/klamke.

Additional details and impacted files

@@              Coverage Diff              @@
##           ss/klamke      #35      +/-   ##
=============================================
+ Coverage      88.92%   89.18%   +0.26%     
=============================================
  Files              8        9       +1     
  Lines           1282     1313      +31     
=============================================
+ Hits            1140     1171      +31     
  Misses           142      142              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[sshin23]

Thank you, @klamike