feat: add group_label to StepContent, is_flow_synced/source_tree_name to StepLibraryResponse

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/schemas/step_library.py

@@ -17,6 +17,7 @@ class StepContent(BaseModel):
     instructions: str = Field(..., min_length=1)
     help_text: Optional[str] = None
     commands: Optional[list[StepCommand]] = None
+    group_label: Optional[str] = None  # Section header this step belongs to (for flow-synced steps)
 
 
 # Base schemas
@@ -59,6 +60,8 @@ class StepLibraryResponse(StepLibraryBase):
     # Computed fields (populated by API)
     category_name: Optional[str] = None
     author_name: Optional[str] = None
+    is_flow_synced: bool = False
+    source_tree_name: Optional[str] = None
 
     class Config:
         from_attributes = True