Global cleanup

[BatyLeo]

Making sure all existing benchmarks and the documentation are in line with the new interface.

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Changes:

• Replace generate_anticipative_solution with generate_anticipative_solver(benchmark)
• Convert generate_baseline_policies return values from positional tuples to named tuples for all benchmarks
• Standardize seed=nothing default in generate_statistical_model for all benchmarks
• Remove redundant per-module re-exports
• Move target_policy application out of generate_sample and into generate_dataset exclusively
• Docs: restructure using_benchmarks.md with a "Core workflow" section up front + trim custom_benchmarks.md

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
src/Argmax/Argmax.jl	100.00% <100.00%> (ø)
src/DecisionFocusedLearningBenchmarks.jl	100.00% <ø> (ø)
src/DynamicAssortment/DynamicAssortment.jl	100.00% <100.00%> (ø)
...namicVehicleScheduling/DynamicVehicleScheduling.jl	100.00% <100.00%> (+18.51%)	⬆️
src/FixedSizeShortestPath/FixedSizeShortestPath.jl	94.00% <ø> (ø)
src/Maintenance/Maintenance.jl	100.00% <100.00%> (ø)
src/PortfolioOptimization/PortfolioOptimization.jl	91.89% <ø> (ø)
src/SubsetSelection/SubsetSelection.jl	100.00% <100.00%> (ø)
src/Utils/Utils.jl	100.00% <ø> (ø)
src/Utils/interface.jl	71.92% <100.00%> (-0.49%)	⬇️
... and 1 more

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