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_git.py

@@ -0,0 +1,160 @@
+"""Integration tests for workspace git endpoints."""
+
+import asyncio
+import os
+import subprocess
+import tempfile
+import uuid
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from src.models import GitRepository, Project, Workspace
+
+
+def _run_git(*args: str, cwd: str) -> None:
+    subprocess.run(["git", *args], cwd=cwd, check=True, capture_output=True)
+
+
+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_repo_with_git_workspace(
+    db_session: AsyncSession, authenticated_client: TestClient
+):
+    """Create a workspace backed by a real git repo with commits."""
+    user_id = _get_user_id(authenticated_client)
+
+    async def _create():
+        project = Project(name="Git Test Project", owner_id=user_id)
+        db_session.add(project)
+        await db_session.flush()
+
+        repo = GitRepository(
+            name="git-test-repo",
+            path="/tmp/git-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()
+        _run_git("init", cwd=tmpdir)
+        _run_git("config", "user.email", "test@test.com", cwd=tmpdir)
+        _run_git("config", "user.name", "Test User", cwd=tmpdir)
+        with open(os.path.join(tmpdir, "README.md"), "w") as f:
+            f.write("# Test\n")
+        _run_git("add", "README.md", cwd=tmpdir)
+        _run_git("commit", "-m", "Initial commit", cwd=tmpdir)
+
+        ws = Workspace(
+            name="dev",
+            repo_id=repo.id,
+            user_id=user_id,
+            branch="main",
+            path=tmpdir,
+        )
+        db_session.add(ws)
+        await db_session.commit()
+        await db_session.refresh(ws)
+        return ws
+
+    return asyncio.run(_create())
+
+
+class TestGitStatus:
+    """Tests for GET /workspaces/{id}/git/status."""
+
+    def test_status_clean(
+        self, authenticated_client: TestClient, test_repo_with_git_workspace: Workspace
+    ):
+        response = authenticated_client.get(
+            f"/workspaces/{test_repo_with_git_workspace.id}/git/status"
+        )
+        assert response.status_code == 200
+        data = response.json()
+        assert data["branch"] == "main"
+        assert data["modified"] == []
+
+    def test_status_modified(
+        self, authenticated_client: TestClient, test_repo_with_git_workspace: Workspace
+    ):
+        with open(os.path.join(test_repo_with_git_workspace.path, "README.md"), "a") as f:
+            f.write("modified\n")
+
+        response = authenticated_client.get(
+            f"/workspaces/{test_repo_with_git_workspace.id}/git/status"
+        )
+        assert response.status_code == 200
+        assert "README.md" in response.json()["modified"]
+
+
+class TestGitCommit:
+    """Tests for POST /workspaces/{id}/git/commit."""
+
+    def test_commit(
+        self, authenticated_client: TestClient, test_repo_with_git_workspace: Workspace
+    ):
+        with open(os.path.join(test_repo_with_git_workspace.path, "new.py"), "w") as f:
+            f.write("print('hello')\n")
+
+        response = authenticated_client.post(
+            f"/workspaces/{test_repo_with_git_workspace.id}/git/commit",
+            json={"message": "Add new file"},
+        )
+        assert response.status_code == 200
+        assert response.json()["status"] == "committed"
+
+    def test_commit_missing_message(
+        self, authenticated_client: TestClient, test_repo_with_git_workspace: Workspace
+    ):
+        response = authenticated_client.post(
+            f"/workspaces/{test_repo_with_git_workspace.id}/git/commit",
+            json={},
+        )
+        assert response.status_code == 400
+
+
+class TestGitHistory:
+    """Tests for GET /workspaces/{id}/git/history."""
+
+    def test_history(
+        self, authenticated_client: TestClient, test_repo_with_git_workspace: Workspace
+    ):
+        response = authenticated_client.get(
+            f"/workspaces/{test_repo_with_git_workspace.id}/git/history"
+        )
+        assert response.status_code == 200
+        data = response.json()
+        assert len(data["commits"]) >= 1
+        assert data["commits"][0]["message"] == "Initial commit"
+
+
+class TestGitCheckout:
+    """Tests for POST /workspaces/{id}/git/checkout."""
+
+    def test_checkout(
+        self, authenticated_client: TestClient, test_repo_with_git_workspace: Workspace
+    ):
+        _run_git("checkout", "-b", "feature", cwd=test_repo_with_git_workspace.path)
+        _run_git("checkout", "main", cwd=test_repo_with_git_workspace.path)
+
+        response = authenticated_client.post(
+            f"/workspaces/{test_repo_with_git_workspace.id}/git/checkout",
+            json={"branch": "feature"},
+        )
+        assert response.status_code == 200
+        assert response.json()["branch"] == "feature"