test(server): normalize expected cwd in worktree grouping test

classifyDirectoryForProjectMembership normalizes input.cwd via
path.resolve, which on Windows turns "/tmp/repo-feature" into
"D:\\tmp\\repo-feature". Mirror existing pattern (deriveWorkspaceId
tests at lines 91/107) and wrap the expected cwd with
normalizeWorkspaceId so the test passes on both POSIX and Windows.

packages/server/src/server/workspace-registry-model.test.ts

@@ -124,7 +124,7 @@ describe("git worktree grouping", () => {
     });
 
     expect(membership).toMatchObject({
-      cwd: "/tmp/repo-feature",
+      cwd: normalizeWorkspaceId("/tmp/repo-feature"),
       workspaceId: "/tmp/repo-feature",
       workspaceKind: "worktree",
       workspaceDisplayName: "feature/plain",