Fix documentation to use proper method signatures for System dispatch

Updated @docs blocks in docs/src/API/problems.md to use proper Documenter.jl
method signature syntax to catch ModelingToolkit's specific method dispatches.

Now using explicit method signatures like:
- SciMLBase.ODEProblem(::System, ::Any, ::Any)
- SciMLBase.NonlinearProblem(::System, ::Any)
- SciMLBase.OptimizationProblem(::System, ::Any)

This ensures that Documenter.jl will find and display ModelingToolkit's enhanced
docstrings that include references to both MTK's problem building documentation
and the relevant solver documentation, instead of showing the generic SciMLBase
docstrings.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: claude

docs/src/API/problems.md

@@ -14,41 +14,41 @@ code for a variety of such numerical problems.
 
 ```@docs
 SciMLBase.ODEFunction
-ODEProblem
+SciMLBase.ODEProblem(::System, ::Any, ::Any)
 SciMLBase.DAEFunction
-SciMLBase.DAEProblem
+SciMLBase.DAEProblem(::System, ::Any, ::Any)
 SciMLBase.SDEFunction
-SDEProblem
+SciMLBase.SDEProblem(::System, ::Any, ::Any)
 SciMLBase.DDEFunction
-SciMLBase.DDEProblem
+SciMLBase.DDEProblem(::System, ::Any, ::Any)
 SciMLBase.SDDEFunction
 SciMLBase.SDDEProblem
-JumpProblem
-SciMLBase.BVProblem
-DiscreteProblem
-ImplicitDiscreteProblem
+JumpProcesses.JumpProblem(::System, ::Any, ::Any)
+SciMLBase.BVProblem(::System, ::Any, ::Any)
+SciMLBase.DiscreteProblem
+SciMLBase.ImplicitDiscreteProblem
 ```
 
 ## Linear and Nonlinear systems
 
 ```@docs
 SciMLBase.NonlinearFunction
-NonlinearProblem
+SciMLBase.NonlinearProblem(::System, ::Any)
 SciMLBase.SCCNonlinearProblem
 SciMLBase.NonlinearLeastSquaresProblem
-SteadyStateProblem
+DiffEqBase.SteadyStateProblem(::System, ::Any)
 SciMLBase.IntervalNonlinearFunction
-IntervalNonlinearProblem
+SciMLBase.IntervalNonlinearProblem
 ModelingToolkit.HomotopyContinuationProblem
 SciMLBase.HomotopyNonlinearFunction
-SciMLBase.LinearProblem
+SciMLBase.LinearProblem(::System, ::Any)
 ```
 
 ## Optimization and optimal control
 
 ```@docs
 SciMLBase.OptimizationFunction
-OptimizationProblem
+SciMLBase.OptimizationProblem(::System, ::Any)
 SciMLBase.ODEInputFunction
 ModelingToolkit.JuMPDynamicOptProblem
 ModelingToolkit.InfiniteOptDynamicOptProblem