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/compat.py

@@ -0,0 +1,43 @@
+"""Shared Pydantic field helpers for workplan / workstream compatibility."""
+from __future__ import annotations
+
+import uuid
+
+from pydantic import AliasChoices, Field, computed_field, model_validator
+
+
+def workplan_id_field(*, default: uuid.UUID | None = None) -> uuid.UUID | None:
+    return Field(
+        default=default,
+        validation_alias=AliasChoices("workplan_id", "workstream_id"),
+    )
+
+
+class WorkplanIdCompatMixin:
+    """Accept ``workplan_id`` or legacy ``workstream_id`` on input; emit both on output."""
+
+    workplan_id: uuid.UUID = workplan_id_field()
+
+    @computed_field  # type: ignore[prop-decorator]
+    @property
+    def workstream_id(self) -> uuid.UUID:
+        return self.workplan_id
+
+
+class WorkplanIdCreateMixin:
+    workplan_id: uuid.UUID | None = workplan_id_field(default=None)
+
+    @model_validator(mode="after")
+    def _require_workplan_id(self):
+        if self.workplan_id is None:
+            raise ValueError("workplan_id is required")
+        return self
+
+
+class OptionalWorkplanIdCompatMixin:
+    workplan_id: uuid.UUID | None = workplan_id_field(default=None)
+
+    @computed_field  # type: ignore[prop-decorator]
+    @property
+    def workstream_id(self) -> uuid.UUID | None:
+        return self.workplan_id