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/unit/test_git_operations.py

@@ -0,0 +1,133 @@
+"""Unit tests for GitOperations."""
+
+import asyncio
+import os
+import subprocess
+import tempfile
+
+import pytest
+
+from src.models import Workspace
+from src.services.git.git_operations import GitOperations
+
+
+def _run_git(*args: str, cwd: str) -> None:
+    subprocess.run(["git", *args], cwd=cwd, check=True, capture_output=True)
+
+
+@pytest.fixture
+def temp_workspace():
+    """Create a temporary git workspace."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        _run_git("init", cwd=tmpdir)
+        _run_git("config", "user.email", "test@test.com", cwd=tmpdir)
+        _run_git("config", "user.name", "Test User", cwd=tmpdir)
+
+        readme = os.path.join(tmpdir, "README.md")
+        with open(readme, "w") as f:
+            f.write("# Test\n")
+        _run_git("add", "README.md", cwd=tmpdir)
+        _run_git("commit", "-m", "Initial commit", cwd=tmpdir)
+
+        ws = Workspace(
+            id="00000000-0000-0000-0000-000000000001",
+            name="test-ws",
+            repo_id="00000000-0000-0000-0000-000000000002",
+            user_id="00000000-0000-0000-0000-000000000003",
+            branch="main",
+            path=tmpdir,
+        )
+        yield ws
+
+
+class TestGitOperationsStatus:
+    """Tests for GitOperations.status."""
+
+    def test_status_clean(self, temp_workspace: Workspace):
+        git = GitOperations(temp_workspace)
+        status = asyncio.run(git.status())
+        assert status.branch == "main"
+        assert status.modified == []
+        assert status.added == []
+        assert status.deleted == []
+        assert status.untracked == []
+
+    def test_status_modified(self, temp_workspace: Workspace):
+        with open(os.path.join(temp_workspace.path, "README.md"), "a") as f:
+            f.write("modified\n")
+
+        git = GitOperations(temp_workspace)
+        status = asyncio.run(git.status())
+        assert "README.md" in status.modified
+
+    def test_status_untracked(self, temp_workspace: Workspace):
+        with open(os.path.join(temp_workspace.path, "new.py"), "w") as f:
+            f.write("print('hello')\n")
+
+        git = GitOperations(temp_workspace)
+        status = asyncio.run(git.status())
+        assert "new.py" in status.untracked
+
+
+class TestGitOperationsCommit:
+    """Tests for GitOperations.commit."""
+
+    def test_commit_stages_and_commits(self, temp_workspace: Workspace):
+        with open(os.path.join(temp_workspace.path, "new.py"), "w") as f:
+            f.write("print('hello')\n")
+
+        git = GitOperations(temp_workspace)
+        asyncio.run(git.commit("Add new file"))
+
+        status = asyncio.run(git.status())
+        assert "new.py" not in status.untracked
+        assert "new.py" not in status.added
+
+        history = asyncio.run(git.history())
+        assert history[0].message == "Add new file"
+
+    def test_commit_fails_without_changes(self, temp_workspace: Workspace):
+        git = GitOperations(temp_workspace)
+        with pytest.raises(RuntimeError):
+            asyncio.run(git.commit("Nothing to commit"))
+
+
+class TestGitOperationsHistory:
+    """Tests for GitOperations.history."""
+
+    def test_history_returns_commits(self, temp_workspace: Workspace):
+        git = GitOperations(temp_workspace)
+        history = asyncio.run(git.history())
+        assert len(history) >= 1
+        assert history[0].message == "Initial commit"
+
+    def test_history_filters_by_path(self, temp_workspace: Workspace):
+        with open(os.path.join(temp_workspace.path, "new.py"), "w") as f:
+            f.write("print('hello')\n")
+
+        git = GitOperations(temp_workspace)
+        asyncio.run(git.commit("Add new file"))
+
+        history = asyncio.run(git.history(path="new.py"))
+        assert len(history) == 1
+        assert history[0].message == "Add new file"
+
+
+class TestGitOperationsBranches:
+    """Tests for GitOperations.branches."""
+
+    def test_branches_lists_main(self, temp_workspace: Workspace):
+        git = GitOperations(temp_workspace)
+        branches, current = asyncio.run(git.branches())
+        assert "main" in branches
+        assert current == "main"
+
+    def test_checkout_switches_branch(self, temp_workspace: Workspace):
+        _run_git("checkout", "-b", "feature", cwd=temp_workspace.path)
+        _run_git("checkout", "main", cwd=temp_workspace.path)
+
+        git = GitOperations(temp_workspace)
+        asyncio.run(git.checkout("feature"))
+
+        status = asyncio.run(git.status())
+        assert status.branch == "feature"