ProblemAdapter dispatch depends on import order of `optimize4` and `meshgen`

Summary

ProblemAdapter(problem, field) fails with a multiple-dispatch error when optimize4 is imported before meshgen. The same code succeeds if the import order is reversed.

Minimal Example

import optimize4
import meshgen

var dom = CircularDomain([0,0], 1)
var mg = MeshGen(dom, [-1..1:0.2, -1..1:0.2])
var mesh = ChangeMeshDimension(mg.build(), 3)

var u = Field(mesh, 1)

fn energyDensity(x, u) {
    return u*u
}

var problem = OptimizationProblem(mesh)
var energy = AreaIntegral(energyDensity, u)
problem.addenergy(energy)

print "About to construct ProblemAdapter(problem, u)..."
var adapter = ProblemAdapter(problem, u)
print "ProblemAdapter constructed successfully: ${adapter}"

Actual behavior

The script fails with:

About to construct ProblemAdapter(problem, u)...
Error 'MltplDsptchFld': Multiple dispatch could not find an implementation that matches these arguments.
  from global at line 34

Expected behavior

ProblemAdapter(problem, u) should construct a valid adapter, independent of whether optimize4 or meshgen is imported first.

Workaround

Changing the import order fixes the issue:

import meshgen
import optimize4

Reproduce the minimal example with both import orders, focusing on ProblemAdapter(problem, u) and the MltplDsptchFld error. Inspect how optimize4 and meshgen register the relevant multiple-dispatch implementations. Done means ProblemAdapter constructs successfully regardless of which module is imported first.