Creating an unowned CmPossibilityList issues no PropChanged

从 UnitOfWorkService.cs、Virtuals.cs、CmObject.cs 和 FactoryAdditions.cs 开始，将 LexEntry 和 Text 的 virtual-notification 实现与 CreateUnowned 路径进行比较。跟踪 SetDefaultValuesAfterInit 和 OnBeforeObjectDeleted，包括 bootstrap guard，然后验证创建或删除无所有者的 CmPossibilityList 是否会产生预期的 PropChanged 通知，以及是否使用了无所有者的 Factory 初始化路径。

Gap

IUnitOfWorkService.RegisterObjectAsCreated (src/SIL.LCModel/Infrastructure/Impl/UnitOfWorkService.cs:583) records creation as an LcmStateChangeObjectCreation (src/SIL.LCModel/Infrastructure/Impl/LcmStateChangingClasses.cs:279). That class derives from LcmStateChangeBase and does not implement ILcmPropertyChanged. UnitOfWork.GetPropChangeInformation (src/SIL.LCModel/Infrastructure/Impl/UnitOfWork.cs:621) yields only from actions that implement ILcmPropertyChanged, so object creation by itself produces no ChangeInformation.

For an owned object the PropChanged arrives from the owning property's LcmVectorPropertyChanged / LcmAtomicRefPropertyChanged. An unowned object has no owning property, so no IVwNotifyChange.PropChanged is issued at all. This is the open TODO at UnitOfWorkService.cs:599:

// (TODO: What needs to be done for unowned objects?)

ICmPossibilityListFactory.CreateUnowned (src/SIL.LCModel/DomainImpl/FactoryAdditions.cs:1560) hits this. The new CmPossibilityList is registered in the IdentityMap, is returned by ICmPossibilityListRepository.AllInstances(), and is persisted as a UOW newbie — but no client receives a PropChanged, so nothing that caches a view of the lists is told to reload.

Proposed fix

Apply the pattern already used for the other unowned classes:

• LexEntry.RegisterVirtualsModifiedForObjectCreation (src/SIL.LCModel/DomainImpl/OverridesLing_Lex.cs:854) → Virtuals.LexDbEntries
• Text.RegisterVirtualsModifiedForObjectCreation / ...ForObjectDeletion (src/SIL.LCModel/DomainImpl/OverridesLing_Wfi.cs:1713 and :1746) → Virtuals.LangProjTexts

1. Add a Virtuals accessor for LangProject.AllPossibilityLists, which already exists as a virtual property (src/SIL.LCModel/DomainImpl/OverridesLangProj.cs:83, declared [VirtualProperty(CellarPropertyType.ReferenceCollection, "CmPossibilityList")]). Model it on Virtuals.LangProjTexts (src/SIL.LCModel/DomainImpl/Virtuals.cs:205).

2. On CmPossibilityList, override RegisterVirtualsModifiedForObjectCreation and RegisterVirtualsModifiedForObjectDeletion (src/SIL.LCModel/DomainImpl/CmObject.cs:1758 and :1769) to call uow.RegisterVirtualCollectionAsModified for that flid on Cache.LangProject, and invoke them from SetDefaultValuesAfterInit / OnBeforeObjectDeleted the way Text does.

3. Make CmPossibilityListFactory.CreateUnowned call ((ICmObjectInternal)result).InitializeNewOwnerlessCmObjectWithPresetGuid() before returning, matching the generated ownerless CmPossibilityListFactory.Create(Guid) (src/SIL.LCModel/DomainImpl/GeneratedFactoryImplementations.cs:320-327). Without this, SetDefaultValuesAfterInit never runs on the CreateUnowned path and the hook added in step 2 would not fire.

ChangeReconciler.ReconcileForeignChanges already calls RegisterVirtualsModifiedForObjectCreation on each foreign newby (src/SIL.LCModel/Infrastructure/Impl/ChangeReconciler.cs:212), so step 2 also covers Send/Receive and second-window reconciliation.

Note that SetDefaultValuesAfterInit also runs during bootstrap and data migration, where Cache.LangProject may not be resolvable; LexEntry and Text carry the same exposure, so follow whatever guard they rely on.

Out of scope

Custom field metadata is a separate mechanism with no notification path at all: LcmMetaDataCache.AddCustomField / UpdateCustomField / DeleteCustomField mutate m_metaFieldRecords in place, and FieldDescription.UpdateCustomField registers affected objects as modified but registers no metadata change. Clients must continue to be notified manually after adding a custom field.