Jd/bin2 approx

[jd-lara]

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[Copilot]

Pull request overview

Adds a Bin2-style bilinear product approximation (z ≈ x·y) to the existing quadratic-approximation tooling by decomposing into two squared terms via the difference-of-squares identity, with an optional McCormick envelope for additional bounding, plus a new dedicated unit test file.

Changes:

• Add McCormick envelope constraints helper for bilinear products.
• Add bilinear approximation helpers that reuse existing SOS2/manual-SOS2/sawtooth quadratic approximations on (x+y)² and (x−y)².
• Add unit tests covering container structure, basic correctness cases, and approximation behavior for the three bilinear variants.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/quadratic_approximations/mccormick.jl	Introduces McCormickConstraint and _add_mccormick_envelope! for optional linear envelopes around z = x·y.
src/quadratic_approximations/bilinear.jl	Adds Bin2 bilinear approximation implementation and three wrappers (solver SOS2, manual SOS2, sawtooth), reusing quadratic approximation functions.
src/InfrastructureOptimizationModels.jl	Includes the new McCormick and bilinear approximation source files in the main module.
test/test_bilinear_approximations.jl	New test suite for bilinear approximations (structure + solve-based checks).
test/InfrastructureOptimizationModelsTests.jl	Wires the new bilinear test file into the unit test runner.

Comments suppressed due to low confidence (2)

test/test_bilinear_approximations.jl:5

• _setup_bilinear_test depends on _setup_qa_container being defined by another test file (currently test_quadratic_approximations.jl) and on include ordering in InfrastructureOptimizationModelsTests.jl. This makes the test file non-self-contained and can break if test include order changes or if this test is run in isolation. Consider moving shared setup helpers into a dedicated test_utils include (or redefining the needed helpers locally) so each test file is independent.

function _setup_bilinear_test(device_names::Vector{String}, time_steps::UnitRange{Int})
    container = _setup_qa_container(time_steps)
    x_var_container = IOM.add_variable_container!(

test/test_bilinear_approximations.jl:370

• This test file uses MOI.SOS2{Float64} but does not define/import MOI locally (it currently relies on const MOI = JuMP.MOI from another included test file). To avoid cross-test coupling, reference JuMP.MOI directly here or add const MOI = JuMP.MOI in this file.

            sos2_count = JuMP.num_constraints(
                setup.jump_model,
                Vector{JuMP.VariableRef},
                MOI.SOS2{Float64},
            )

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