Task flow engine implementation

api/schemas/workstream.py

@@ -1,18 +1,20 @@
 import uuid
 from datetime import date, datetime
+from typing import Literal
 
 from pydantic import BaseModel, ConfigDict
 
-from api.models.workstream import WorkstreamStatus
 from api.schemas.workstream_dependency import WorkstreamDepStub
 
+WorkstreamStatus = Literal["todo", "active", "blocked", "completed", "archived"]
+
 
 class WorkstreamCreate(BaseModel):
     topic_id: uuid.UUID
     slug: str
     title: str
     description: str | None = None
-    status: WorkstreamStatus = WorkstreamStatus.active
+    status: WorkstreamStatus = "active"
     owner: str | None = None
     due_date: date | None = None
     repo_id: uuid.UUID | None = None  # GEMS primary: the owning repository
@@ -57,3 +59,4 @@ class WorkstreamWithDeps(WorkstreamWithTaskCounts):
     """WorkstreamWithTaskCounts enriched with dependency graph edges."""
     depends_on: list[WorkstreamDepStub] = []
     blocks: list[WorkstreamDepStub] = []
+    blocked_reasons: list[dict] = []