feat: reconcile legacy message identities

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a0230c-b06c-7641-808a-e191b6d1da49

hub_core/migrations/versions/0005_message_identity_aliases.py

@@ -0,0 +1,51 @@
+"""governed legacy message identity aliases
+
+Revision ID: 0005_message_identity_aliases
+Revises: 0004_workload_projection
+Create Date: 2026-08-23
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy.dialects import postgresql
+
+revision: str = "0005_message_identity_aliases"
+down_revision: Union[str, None] = "0004_workload_projection"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "agent_message_identity_aliases",
+        sa.Column("alias", sa.String(255), primary_key=True),
+        sa.Column(
+            "message_id",
+            postgresql.UUID(as_uuid=True),
+            sa.ForeignKey("agent_messages.id", ondelete="RESTRICT"),
+            nullable=False,
+        ),
+        sa.Column("source", sa.String(255), nullable=False),
+        sa.Column("reason", sa.Text(), nullable=False),
+        sa.Column("created_by", sa.String(100), nullable=False),
+        sa.Column(
+            "created_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.text("now()"),
+            nullable=False,
+        ),
+    )
+    op.create_index(
+        "ix_agent_message_identity_aliases_message_id",
+        "agent_message_identity_aliases",
+        ["message_id"],
+    )
+
+
+def downgrade() -> None:
+    op.drop_index(
+        "ix_agent_message_identity_aliases_message_id",
+        table_name="agent_message_identity_aliases",
+    )
+    op.drop_table("agent_message_identity_aliases")