feat(agent): complete closed-loop runtime and pricing fallback

backend/src/models/agent_chat_message.py

@@ -45,7 +45,10 @@ class AgentChatMessage(TimestampMixin, SoftDeleteMixin, Base):
     seq: Mapped[int] = mapped_column(Integer, nullable=False)
     role: Mapped[AgentChatMessageRole] = mapped_column(
         SqlEnum(
-            AgentChatMessageRole, name="agent_chat_message_role", native_enum=False
+            AgentChatMessageRole,
+            name="agent_chat_message_role",
+            native_enum=False,
+            values_callable=lambda enum_cls: [item.value for item in enum_cls],
         ),
         nullable=False,
     )

backend/src/models/agent_chat_session.py

@@ -7,6 +7,7 @@ from enum import Enum
 
 from sqlalchemy import (
     DateTime,
+    JSON,
     Enum as SqlEnum,
     Integer,
     Numeric,
@@ -56,7 +57,10 @@ class AgentChatSession(TimestampMixin, SoftDeleteMixin, Base):
     title: Mapped[str | None] = mapped_column(String(255), nullable=True)
     status: Mapped[AgentChatSessionStatus] = mapped_column(
         SqlEnum(
-            AgentChatSessionStatus, name="agent_chat_session_status", native_enum=False
+            AgentChatSessionStatus,
+            name="agent_chat_session_status",
+            native_enum=False,
+            values_callable=lambda enum_cls: [item.value for item in enum_cls],
         ),
         nullable=False,
         default=AgentChatSessionStatus.PENDING,
@@ -76,6 +80,6 @@ class AgentChatSession(TimestampMixin, SoftDeleteMixin, Base):
         Numeric(12, 6), nullable=False, server_default=text("0")
     )
     state_snapshot: Mapped[dict | None] = mapped_column(
-        JSONB,
+        JSON().with_variant(JSONB, "postgresql"),
         nullable=True,
     )

backend/src/models/system_agents.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 
 import uuid
 
-from sqlalchemy import ForeignKey, String
+from sqlalchemy import JSON, ForeignKey, String
 from sqlalchemy.dialects.postgresql import JSONB, UUID
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -26,7 +26,7 @@ class SystemAgents(TimestampMixin, Base):
         nullable=False,
     )
     config: Mapped[dict] = mapped_column(
-        JSONB,
+        JSON().with_variant(JSONB, "postgresql"),
         nullable=False,
         server_default="{}",
     )