feat: complete working-copies workspace-first cleanup

- Remove clone_mode/branch/new_branch from frontend create session flow.
- Add workspace picker to CreateSessionForm; auto-create default workspace when repo selected.
- Fix tool-starter.tsx and use-start-tool.ts createInstance signatures after API change.
- Remove clone mode badge from SessionCard.
- Delete stale backend unit tests referencing removed clone_mode schema fields.
- Update OpenSpec working-copies tasks and mark change completed.
- Regenerate project maps.

Quality gates: npm run typecheck, npm run lint, npm test -- --run (82 passed),
python3 -m py_compile on changed backend files.

apps/api/tests/unit/test_session_branch_selection.py

@@ -1,179 +0,0 @@
-"""Tests for session creation with branch selection and new branch creation."""
-
-import os
-import subprocess
-import tempfile
-
-
-from src.api.tool_instances import CreateInstanceRequest
-
-
-class TestCreateInstanceRequest:
-    """Tests for CreateInstanceRequest model."""
-
-    def test_default_values(self):
-        """Test default values for CreateInstanceRequest."""
-        request = CreateInstanceRequest(tool_type_id="123")
-        assert request.clone_mode == "mount"
-        assert request.branch == "main"
-        assert request.new_branch is None
-        assert request.display_name is None
-
-    def test_clone_mode_with_branch(self):
-        """Test CreateInstanceRequest with clone mode and branch."""
-        request = CreateInstanceRequest(
-            tool_type_id="123",
-            clone_mode="clone",
-            branch="dev",
-        )
-        assert request.clone_mode == "clone"
-        assert request.branch == "dev"
-
-    def test_new_branch_field(self):
-        """Test CreateInstanceRequest with new_branch field."""
-        request = CreateInstanceRequest(
-            tool_type_id="123",
-            clone_mode="clone",
-            branch="main",
-            new_branch="feature/test",
-        )
-        assert request.new_branch == "feature/test"
-
-
-class TestBranchCreationInClone:
-    """Tests for branch creation logic in clone process."""
-
-    def test_create_local_branch_success(self):
-        """Test successful local branch creation."""
-        with tempfile.TemporaryDirectory() as tmpdir:
-            # Initialize repo
-            subprocess.run(
-                ["git", "init", tmpdir],
-                capture_output=True,
-                check=True,
-            )
-            subprocess.run(
-                ["git", "-C", tmpdir, "config", "user.email", "test@test.com"],
-                capture_output=True,
-                check=True,
-            )
-            subprocess.run(
-                ["git", "-C", tmpdir, "config", "user.name", "Test User"],
-                capture_output=True,
-                check=True,
-            )
-            
-            # Create initial commit
-            readme = os.path.join(tmpdir, "README.md")
-            with open(readme, "w") as f:
-                f.write("# Test\n")
-            subprocess.run(
-                ["git", "-C", tmpdir, "add", "README.md"],
-                capture_output=True,
-                check=True,
-            )
-            subprocess.run(
-                ["git", "-C", tmpdir, "commit", "-m", "Initial commit"],
-                capture_output=True,
-                check=True,
-            )
-            
-            # Create new branch
-            result = subprocess.run(
-                ["git", "-C", tmpdir, "checkout", "-b", "feature/new-branch"],
-                capture_output=True,
-                text=True,
-            )
-            
-            assert result.returncode == 0
-            
-            # Verify branch exists
-            branches_result = subprocess.run(
-                ["git", "-C", tmpdir, "branch", "--show-current"],
-                capture_output=True,
-                text=True,
-            )
-            assert branches_result.stdout.strip() == "feature/new-branch"
-
-    def test_create_local_branch_invalid_name(self):
-        """Test local branch creation with invalid name fails."""
-        with tempfile.TemporaryDirectory() as tmpdir:
-            # Initialize repo
-            subprocess.run(
-                ["git", "init", tmpdir],
-                capture_output=True,
-                check=True,
-            )
-            subprocess.run(
-                ["git", "-C", tmpdir, "config", "user.email", "test@test.com"],
-                capture_output=True,
-                check=True,
-            )
-            subprocess.run(
-                ["git", "-C", tmpdir, "config", "user.name", "Test User"],
-                capture_output=True,
-                check=True,
-            )
-            
-            # Create initial commit
-            readme = os.path.join(tmpdir, "README.md")
-            with open(readme, "w") as f:
-                f.write("# Test\n")
-            subprocess.run(
-                ["git", "-C", tmpdir, "add", "README.md"],
-                capture_output=True,
-                check=True,
-            )
-            subprocess.run(
-                ["git", "-C", tmpdir, "commit", "-m", "Initial commit"],
-                capture_output=True,
-                check=True,
-            )
-            
-            # Try to create branch with invalid name (contains spaces)
-            result = subprocess.run(
-                ["git", "-C", tmpdir, "checkout", "-b", "invalid branch name"],
-                capture_output=True,
-                text=True,
-            )
-            
-            # Git accepts branch names with spaces but it's not recommended
-            # This test verifies the command structure
-            assert result.returncode == 0 or "fatal" in result.stderr
-
-
-class TestCreateInstanceAPI:
-    """Tests for create instance API endpoint with branch options."""
-
-    def test_create_instance_request_validation(self):
-        """Test that CreateInstanceRequest validates correctly."""
-        # Valid request with new_branch
-        request = CreateInstanceRequest(
-            tool_type_id="550e8400-e29b-41d4-a716-446655440000",
-            clone_mode="clone",
-            branch="main",
-            new_branch="feature/test",
-        )
-        assert request.new_branch == "feature/test"
-        
-        # Valid request without new_branch
-        request2 = CreateInstanceRequest(
-            tool_type_id="550e8400-e29b-41d4-a716-446655440000",
-            clone_mode="clone",
-            branch="dev",
-        )
-        assert request2.new_branch is None
-
-    def test_create_instance_with_new_branch_sets_instance_branch(self):
-        """Test that instance branch is set to new_branch when provided."""
-        # This tests the logic: data.new_branch if data.new_branch else data.branch
-        new_branch = "feature/test"
-        base_branch = "main"
-        
-        # Simulate the logic from create_instance
-        stored_branch = new_branch if new_branch else base_branch
-        assert stored_branch == "feature/test"
-        
-        # Without new_branch
-        stored_branch2 = None if None else base_branch
-        assert stored_branch2 == "main"