DriverHostActor.ApplyAndAck now reads the deployment artifact and
reconciles its set of DriverInstanceActor children — spawn the missing,
ApplyDelta to those with changed config, stop the removed/disabled.
The diff lives in pure DriverSpawnPlanner so it can be unit-tested
without an ActorSystem.
Adds IDriverFactory in Core.Abstractions (consumed by Runtime) +
DriverFactoryRegistryAdapter in Core.Hosting that wraps the existing
v1 DriverFactoryRegistry — Runtime stays decoupled from Polly/Serilog,
the Host wires the adapter once driver assemblies have registered.
ShouldStub(type, roles) is now actually called on every spawn — Galaxy
+ Wonderware-Historian boot stubbed on macOS/Linux or whenever the host
carries the dev role. Missing factory ⇒ stub fallback, never a crash.
Tests: 24 → 34 in Runtime (+10):
- DriverSpawnPlannerTests x7 (diff cases, type change ⇒ stop+respawn)
- DeploymentArtifactTests x5 (empty/malformed/missing fields tolerant)
- DriverHostActorReconcileTests x4 (spawn count, stub fallback,
ShouldStub gate, second-apply stops the removed)
All 6 v2 test suites green: 120 tests passing.
Closes F20 (ShouldStub wired). F7 marked partial — subscription
publishing + write path still stubbed in DriverInstanceActor itself.
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