Phase 2: Domänenmodell nach §10.1 (plattformneutral, Pydantic)

- Project/Composition/Layer/Source/EffectInstance/MediaAsset/OutputSurface/
  PresetScene mit schema_version 1 (§10, §24.4)
- Validierungen: 2 Effekt-Slots (§4.1), eindeutige Layer-IDs/Z-Reihenfolge,
  max 64 Layer, in<out-Punkte, speed ±4x (§16.6), portable relative Pfade
  ohne Traversal (§9.1), eindeutige Asset-Pfade (§13.3), Canvas-Bounds bis
  8192 (§3.3), Adjustment/Group ohne Quelle (§12.3)
- OutputSurface mit Canvas-Slice-Modell (§22.2 Mapping-Datenmodell ab V1)
- PresetScene: normalisierter Snapshot + Übergänge V1 (§18.1, §18.3)
- keine Backend-Typen im Modell (§12.6)
- 24 Unit-Tests; Gesamtsuite 223 gruen, Ruff gruen

packages/domain/hms_domain/__init__.py

@@ -2,6 +2,29 @@
 
 from hms_domain.identity import NodeIdentity, NodeRole
 from hms_domain.ids import new_node_id, new_uuid, persistent_node_id
+from hms_domain.model import (
+    DOMAIN_SCHEMA_VERSION,
+    BlendMode,
+    ColorControls,
+    ColorSpace,
+    Composition,
+    Crop,
+    EffectInstance,
+    EffectScope,
+    Layer,
+    LayerType,
+    LoopMode,
+    MediaAsset,
+    OutputSurface,
+    PresetScene,
+    Project,
+    QualityMode,
+    Source,
+    SourceType,
+    Transform2D,
+    TransitionType,
+    TransportState,
+)
 
 __all__ = [
     "new_uuid",
@@ -9,4 +32,25 @@ __all__ = [
     "persistent_node_id",
     "NodeIdentity",
     "NodeRole",
+    "DOMAIN_SCHEMA_VERSION",
+    "Project",
+    "Composition",
+    "Layer",
+    "LayerType",
+    "Source",
+    "SourceType",
+    "EffectInstance",
+    "EffectScope",
+    "BlendMode",
+    "Transform2D",
+    "Crop",
+    "ColorControls",
+    "ColorSpace",
+    "LoopMode",
+    "TransportState",
+    "QualityMode",
+    "MediaAsset",
+    "OutputSurface",
+    "PresetScene",
+    "TransitionType",
 ]