WIP: working-copies backend cleanup

- Remove clone_mode/branch from API responses and make DB columns nullable
- Remove legacy clone-mode branches from create_tool_instance
- Add WORKSPACE_PATH compose variable alongside REPO_PATH
- Add workspace migration helpers in WorkspaceManager

Remaining: POST /workspaces/:id/instances, frontend clone_mode cleanup, tests

apps/api/src/api/tool/sessions.py

@@ -74,8 +74,6 @@ async def get_user_sessions(
                 "workspace_name": workspace_name,
                 "status": instance.status,
                 "url": instance.url,
-                "clone_mode": instance.clone_mode,
-                "branch": instance.branch,
                 "selected_config_profile_id": str(instance.selected_config_profile_id)
                 if instance.selected_config_profile_id
                 else None,

apps/api/src/api/tool/tool_instances.py

@@ -68,8 +68,7 @@ async def create_instance(
         "display_name": instance.display_name,
         "tool_type_id": str(instance.tool_type_id),
         "status": instance.status,
-        "clone_mode": instance.clone_mode,
-        "branch": instance.branch,
+        "workspace_id": str(instance.workspace_id) if instance.workspace_id else None,
         "selected_config_profile_id": str(instance.selected_config_profile_id) if instance.selected_config_profile_id else None,
         "created_at": instance.created_at.isoformat(),
     }
@@ -143,8 +142,6 @@ async def get_instance(
         "container_id": instance.container_id,
         "container_name": instance.container_name,
         "compose_path": instance.compose_path,
-        "clone_mode": instance.clone_mode,
-        "branch": instance.branch,
         "workspace_id": str(instance.workspace_id) if instance.workspace_id else None,
         "selected_config_profile_id": str(instance.selected_config_profile_id) if instance.selected_config_profile_id else None,
         "ssh_key_ids": instance.ssh_key_ids,