CaseValidate/CaseBuild scripts run without Namespace — EnsureNamespace is a no-op

[Giannoudis]

Problem

DerivedCaseValidator.CaseValidate() and DerivedCaseBuilder.CaseBuild() create
CaseChangeRuntimeSettings / CaseRelationRuntimeSettings without setting the
Namespace property. This causes EnsureNamespace(null) to return field names
unchanged (no-op per StringExtensions.EnsureNamespace).

Impact: Any CaseValidate or CaseBuild script that uses short field names
(e.g. HasField("SvNummer"), GetValue("Salary"), InitValue("Target", v))
silently fails — field lookups return false or null because Case.Fields
stores fully qualified names (DE.SvNummer).

This is inconsistent with PayrunProcessorRegulation, which correctly resolves
and sets Namespace from the derived regulation for every WageType/Collector script.

Existing CaseValidate actions were unaffected because they always passed fully
qualified names as string parameters (e.g. DEValidiereSteuerIdNummer("DE.SteuerIdNummer")).

Affected code paths

Class	Method	Settings type
DerivedCaseValidator	CaseValidate	CaseChangeRuntimeSettings
DerivedCaseValidator	CaseRelationValidate	CaseRelationRuntimeSettings
DerivedCaseBuilder	CaseBuild	CaseChangeRuntimeSettings
DerivedCaseBuilder	CaseRelationBuild	CaseRelationRuntimeSettings

Fix

1. Load derived regulations once in the outer async entry point
2. Pass them through the recursion
3. In each script loop, resolve settings.Namespace from the DerivedCase.RegulationId
   (or DerivedCaseRelation.RegulationId)
4. Change PayrollRuntimeSettings.Namespace from init to set

Regression risk

Low — adds the namespace that was always expected but never set.
Existing scripts that use fully qualified names are unaffected.