Avoid BLAS dot in Enzyme lagrangian helper

[ChrisRackauckas-Claude]

What

Avoid LinearAlgebra.dot in the Enzyme-only lagrangian helper used for constrained Hessian generation. The helper now accumulates the constraint contribution explicitly, which avoids the Julia 1.13-rc1/Enzyme ijl_lazy_load_and_lookup derivative failure while preserving the same scalar value.

Note: This PR should be ignored until reviewed by @ChrisRackauckas.

Why

lib/OptimizationBase / Julia pre / Tests - Core is failing on current master before the QA source-path cleanup PR can get a clean run. The failing stack is in OptimizationEnzymeExt.lagrangian through LinearAlgebra.dot.

Observed master failure on 794eef029d3183bfdb20b122bf6b26b969a0875c:

EnzymeNoDerivativeError: No augmented forward pass found for ijl_lazy_load_and_lookup
  dot @ LinearAlgebra/src/blas.jl
  lagrangian @ lib/OptimizationBase/ext/OptimizationEnzymeExt.jl:80

Validation

On a clean worktree at current master plus this commit:

OPTIMIZATION_TEST_GROUP=Core timeout 3600 julia +1.13 --project=lib/OptimizationBase -e 'using Pkg; Pkg.test()'

passed:

Test Summary: | Pass  Total     Time
Core          |  777    777  7m16.2s
Testing OptimizationBase tests passed

Also ran:

julia +1.12 --project=. -e 'import Runic; exit(Runic.main(["--check", "lib/OptimizationBase/ext/OptimizationEnzymeExt.jl"]))'
git diff --check