Fix ActivityDefinition sync for daily triage canary

src/activity_core/models.py

@@ -120,7 +120,10 @@ class InstructionDef(BaseModel):
 class ContextSource(BaseModel):
     """One external data source that the workflow queries to build the context snapshot."""
 
-    name: str = Field(description="Logical name; referenced as 'context.<name>' in templates.")
+    name: str = Field(
+        default="",
+        description="Logical name; referenced as 'context.<name>' in templates.",
+    )
     type: str = Field(description="Source adapter type: 'repo-scoping' | 'state-hub' | etc.")
     query: str = Field(default="", description="Named query to execute against the source.")
     params: dict[str, Any] = Field(default_factory=dict)