feat: complete workspace-first-ui cleanup and tests

- Delete dead repo-workspace code: RepoWorkspacePage, useRepoWorkspace,
  WorkspaceLayout, FileBrowser, old git components (git-toolbar, file-editor,
  commit-panel), and repo-workspace.css.
- Fix stale backend test imports for moved models/services.
- Add GitOperations unit tests.
- Add integration tests for workspace files, git, and instances endpoints.
- Add frontend tests for WorkspaceDetailPage and ProjectCard.
- Update OpenSpec workspace-first-ui tasks and mark change completed.
- Regenerate project maps.

Quality gates: npm run typecheck, npm run lint, npm test -- --run (87 passed),
python3 -m py_compile on changed backend files, pytest backend workspace tests.

apps/api/tests/integration/test_workspace_instances.py

@@ -0,0 +1,151 @@
+"""Integration tests for workspace instance endpoints."""
+
+import asyncio
+import tempfile
+import uuid
+from datetime import datetime
+from unittest.mock import patch
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from src.models import GitRepository, Project, ToolInstance, ToolType, Workspace
+
+
+def _get_user_id(client: TestClient) -> uuid.UUID:
+    from src.auth.session import decode_session_cookie
+    from src.config import Settings
+
+    settings = Settings()
+    cookie = client.cookies.get("session")
+    data = decode_session_cookie(settings=settings, cookie_value=cookie)
+    if not data:
+        raise RuntimeError("No session")
+    return uuid.UUID(data["user_id"])
+
+
+@pytest.fixture
+def test_workspace_with_tool_type(
+    db_session: AsyncSession, authenticated_client: TestClient
+):
+    """Create a project, repo, workspace, and tool type."""
+    user_id = _get_user_id(authenticated_client)
+
+    async def _create():
+        project = Project(name="Instance Test Project", owner_id=user_id)
+        db_session.add(project)
+        await db_session.flush()
+
+        repo = GitRepository(
+            name="instance-test-repo",
+            path="/tmp/instance-test-repo",
+            remote_url="https://example.com/repo.git",
+            project_id=project.id,
+            owner_id=user_id,
+        )
+        db_session.add(repo)
+        await db_session.flush()
+
+        tmpdir = tempfile.mkdtemp()
+        ws = Workspace(
+            name="dev",
+            repo_id=repo.id,
+            user_id=user_id,
+            branch="main",
+            path=tmpdir,
+        )
+        db_session.add(ws)
+        await db_session.flush()
+
+        tool_type = ToolType(
+            name="test-tool",
+            display_name="Test Tool",
+            default_port=8080,
+            category="dev",
+        )
+        db_session.add(tool_type)
+        await db_session.commit()
+        await db_session.refresh(ws)
+        await db_session.refresh(tool_type)
+        return ws, tool_type, project
+
+    return asyncio.run(_create())
+
+
+class TestListWorkspaceInstances:
+    """Tests for GET /workspaces/{id}/instances."""
+
+    def test_list_empty(
+        self, authenticated_client: TestClient, test_workspace_with_tool_type
+    ):
+        ws, _, _ = test_workspace_with_tool_type
+        response = authenticated_client.get(f"/workspaces/{ws.id}/instances")
+        assert response.status_code == 200
+        assert response.json() == []
+
+    def test_list_instances(
+        self,
+        authenticated_client: TestClient,
+        db_session: AsyncSession,
+        test_workspace_with_tool_type,
+    ):
+        ws, tool_type, project = test_workspace_with_tool_type
+
+        async def _create_instance():
+            instance = ToolInstance(
+                name="test-instance",
+                display_name="Test Instance",
+                tool_type_id=tool_type.id,
+                repository_id=ws.repo_id,
+                project_id=project.id,
+                owner_id=ws.user_id,
+                workspace_id=ws.id,
+                status="running",
+            )
+            db_session.add(instance)
+            await db_session.commit()
+
+        asyncio.run(_create_instance())
+
+        response = authenticated_client.get(f"/workspaces/{ws.id}/instances")
+        assert response.status_code == 200
+        data = response.json()
+        assert len(data) == 1
+        assert data[0]["display_name"] == "Test Instance"
+
+
+class TestCreateWorkspaceInstance:
+    """Tests for POST /workspaces/{id}/instances."""
+
+    def test_create_instance(
+        self,
+        authenticated_client: TestClient,
+        test_workspace_with_tool_type,
+    ):
+        ws, tool_type, project = test_workspace_with_tool_type
+        mock_instance = ToolInstance(
+            id=uuid.uuid4(),
+            name="mock-instance",
+            display_name="Mock Instance",
+            tool_type_id=tool_type.id,
+            repository_id=ws.repo_id,
+            project_id=project.id,
+            owner_id=ws.user_id,
+            workspace_id=ws.id,
+            status="pending",
+            created_at=datetime.now(),
+        )
+
+        with patch(
+            "src.api.workspace.workspace_instances.create_tool_instance",
+            return_value=mock_instance,
+        ):
+            response = authenticated_client.post(
+                f"/workspaces/{ws.id}/instances",
+                json={"tool_type_id": str(tool_type.id), "display_name": "New Instance"},
+            )
+            assert response.status_code == 201
+            data = response.json()
+            assert data["display_name"] == "Mock Instance"
+            assert data["status"] == "pending"