feat: Support dedicated TextAnnotationDelta for streaming tool responses

PiperOrigin-RevId: 891895587

Author: Annhiluc

google/genai/_interactions/types/content_delta.py

@@ -59,6 +59,7 @@
     "DeltaFileSearchResult",
     "DeltaFileSearchResultResult",
     "DeltaGoogleMapsResult",
+    "DeltaTextAnnotation",
 ]
 
 
@@ -67,9 +68,6 @@ class DeltaText(BaseModel):
 
     type: Literal["text"]
 
-    annotations: Optional[List[Annotation]] = None
-    """Citation information for model-generated content."""
-
 
 class DeltaImage(BaseModel):
     type: Literal["image"]
@@ -362,6 +360,13 @@ class DeltaGoogleMapsResult(BaseModel):
     """A signature hash for backend validation."""
 
 
+class DeltaTextAnnotation(BaseModel):
+    type: Literal["text_annotation"]
+
+    annotations: Optional[List[Annotation]] = None
+    """Citation information for model-generated content."""
+
+
 Delta: TypeAlias = Annotated[
     Union[
         DeltaText,
@@ -385,6 +390,7 @@ class DeltaGoogleMapsResult(BaseModel):
         DeltaMCPServerToolResult,
         DeltaFileSearchResult,
         DeltaGoogleMapsResult,
+        DeltaTextAnnotation,
     ],
     PropertyInfo(discriminator="type"),
 ]