feat(classification-spine): implement STATE-WP-0065 repo-anchored model

Replace the ad-hoc coordination-domain spine with the Repo Classification
Standard: 14 market domains, classification columns on managed_repos, and
workplans anchored by repo_id (topic_id optional).

- Add Alembic migration d8e9f0a1b2c3 with data backfill and workstream→workplan rename
- Add api/classification.py validation and register-from-classification tooling
- Expose workplan-first REST/MCP surface with legacy workstream aliases
- Add C-24 consistency rule and legacy domain frontmatter mapping
- Update dashboard repos page with category/capability/stake filters
- Update orientation docs; mark STATE-WP-0065 finished

api/schemas/task.py

@@ -5,6 +5,7 @@ from typing import Self
 from pydantic import BaseModel, ConfigDict, field_validator, model_validator
 
 from api.models.task import TaskPriority, TaskStatus
+from api.schemas.compat import WorkplanIdCompatMixin, WorkplanIdCreateMixin
 from api.task_status import normalize_task_status
 
 
@@ -17,8 +18,7 @@ class TaskStatusMixin(BaseModel):
         return normalize_task_status(value)
 
 
-class TaskCreate(TaskStatusMixin):
-    workstream_id: uuid.UUID
+class TaskCreate(TaskStatusMixin, WorkplanIdCreateMixin):
     title: str
     description: str | None = None
     status: TaskStatus = TaskStatus.todo
@@ -96,10 +96,9 @@ class TaskStatusBulkSync(BaseModel):
         return value
 
 
-class TaskRead(TaskStatusMixin):
+class TaskRead(TaskStatusMixin, WorkplanIdCompatMixin):
     model_config = ConfigDict(from_attributes=True)
     id: uuid.UUID
-    workstream_id: uuid.UUID
     title: str
     description: str | None = None
     status: TaskStatus
@@ -114,8 +113,7 @@ class TaskRead(TaskStatusMixin):
     updated_at: datetime
 
 
-class TaskCountRead(TaskStatusMixin):
-    workstream_id: uuid.UUID
+class TaskCountRead(TaskStatusMixin, WorkplanIdCompatMixin):
     status: TaskStatus
     count: int