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/models/workplan_dependency.py

@@ -0,0 +1,75 @@
+import uuid
+
+from sqlalchemy import CheckConstraint, ForeignKey, Index, String, Text, text
+from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from api.models.base import Base, TimestampMixin, new_uuid
+
+
+class WorkplanDependency(Base, TimestampMixin):
+    """Directed dependency edge: `from_workplan` depends on a workplan or task.
+
+    Semantics: the target must reach a satisfactory state before `from_workplan`
+    can fully proceed.  Hard deletes are intentional —
+    removing an edge removes a constraint, not information.
+    """
+
+    __tablename__ = "workplan_dependencies"
+    __table_args__ = (
+        CheckConstraint(
+            "(to_workplan_id IS NOT NULL AND to_task_id IS NULL) "
+            "OR (to_workplan_id IS NULL AND to_task_id IS NOT NULL)",
+            name="ck_wp_dep_exactly_one_target",
+        ),
+        Index(
+            "uq_wp_dep_workplan_target",
+            "from_workplan_id",
+            "to_workplan_id",
+            "relationship_type",
+            unique=True,
+            postgresql_where=text("to_workplan_id IS NOT NULL"),
+        ),
+        Index(
+            "uq_wp_dep_task_target",
+            "from_workplan_id",
+            "to_task_id",
+            "relationship_type",
+            unique=True,
+            postgresql_where=text("to_task_id IS NOT NULL"),
+        ),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), primary_key=True, default=new_uuid
+    )
+    from_workplan_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("workplans.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    to_workplan_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("workplans.id", ondelete="CASCADE"),
+        nullable=True,
+        index=True,
+    )
+    to_task_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("tasks.id", ondelete="CASCADE"),
+        nullable=True,
+        index=True,
+    )
+    relationship_type: Mapped[str] = mapped_column(
+        String(40), nullable=False, default="blocks", server_default="blocks", index=True
+    )
+    description: Mapped[str | None] = mapped_column(Text, nullable=True)
+
+    from_workplan: Mapped["Workplan"] = relationship(  # noqa: F821
+        "Workplan", foreign_keys=[from_workplan_id]
+    )
+    to_workplan: Mapped["Workplan | None"] = relationship(  # noqa: F821
+        "Workplan", foreign_keys=[to_workplan_id]
+    )
+    to_task: Mapped["Task | None"] = relationship("Task", foreign_keys=[to_task_id])  # noqa: F821