Improve tutorial-iss based on critical review

- Fix French error message in MINPACK error handling
- Clarify OrdinaryDiffEq is ODE solver backend for Flow
- Keep both MINPACK and NonlinearSolve solver alternatives without performance claims
- Add initial guess guidance with @extref to direct method examples
- Add Hamiltonian constancy verification to validate PMP satisfaction
- Add explanatory comments to plot function for better understanding
- Fix unused parameter λ in nle! function
- Fix @extref syntax for cross-references
- Fix OptimalControl prefix in tutorial-discretisation
- Update package dependencies

Author: ocots

docs/Project.toml

@@ -26,11 +26,11 @@ DocumenterInterLinks = "1"
 ForwardDiff = "0.10, 1"
 LinearAlgebra = "1"
 MINPACK = "1"
-MadNLP = "0.8"
+MadNLP = "0.9"
 NLPModels = "0.21"
 NLPModelsIpopt = "0.11"
 NonlinearSolve = "4"
-OptimalControl = "1"
+OptimalControl = "2"
 OrdinaryDiffEq = "6"
 Plots = "1"
 Printf = "1"