fix: add from __future__ import annotations to workspace_manager.py

Fixes NameError: ToolInstance not defined at runtime because
type annotations are evaluated at class definition time.
Deferring annotation evaluation with __future__ annotations
keeps TYPE_CHECKING imports from causing runtime crashes.

Also includes ruff formatting cleanup on workspace-related files.

apps/api/src/api/tool_instances.py

@@ -1684,6 +1684,7 @@ async def start_instance(
         repo_path = ""
         if instance.workspace_id:
             from src.models.workspace import Workspace as WorkspaceModel
+
             workspace = await session.get(WorkspaceModel, instance.workspace_id)
             if workspace:
                 repo_path = workspace.path

apps/api/src/api/workspaces.py

@@ -108,7 +108,9 @@ async def create_workspace(
         "branch": workspace.branch,
         "path": workspace.path,
         "status": workspace.status,
-        "created_at": workspace.created_at.isoformat() if workspace.created_at else None,
+        "created_at": workspace.created_at.isoformat()
+        if workspace.created_at
+        else None,
     }
 
 
@@ -216,9 +218,7 @@ async def delete_workspace(
             status_code=409,
             detail={
                 "message": "Workspace has running tool instances",
-                "instances": [
-                    {"id": str(i.id), "name": i.name} for i in exc.instances
-                ],
+                "instances": [{"id": str(i.id), "name": i.name} for i in exc.instances],
             },
         ) from exc
     except Exception as exc:

apps/api/src/services/workspace_manager.py

@@ -1,5 +1,7 @@
 """Workspace lifecycle management service."""
 
+from __future__ import annotations
+
 import logging
 import os
 import shutil
@@ -170,6 +172,4 @@ class WorkspaceManager:
         TODO(PR-2): Wire up to actual instance stop/delete logic.
         For now, this is a placeholder.
         """
-        logger.warning(
-            "Placeholder: stopping and deleting instance %s", instance.id
-        )
+        logger.warning("Placeholder: stopping and deleting instance %s", instance.id)