test: run the sidebar markdown and close-workspaces dialog tests

[arzafran]

What this does

Two test files were in the repo but never ran, because they were missing from the Xcode project. This adds them so CI runs them. One of them talked to the app through the old socket protocol that no longer exists, so it is updated to the current one.

Summary

• project.pbxproj: adds programaTests/SidebarMarkdownRendererTests.swift to the unit test target and programaUITests/CloseWorkspacesConfirmDialogUITests.swift to the UI test target (4 entries each).
• CloseWorkspacesConfirmDialogUITests.swift (contract change): the removed v1 line commands (ping, new_workspace, list_workspaces, select_workspace) become v2 JSON-RPC calls (system.ping, workspace.create, workspace.list, workspace.select). Adds the socket-controlled launch setup copied from SidebarHelpMenuUITests. No assertion changed: both tests still check the alert appears and Cancel keeps the workspace counts.
• SidebarMarkdownRendererTests.swift: unchanged.

Follow-up, not in this PR: SidebarHelpMenuUITests.swift:760-762 still sends a v1 ping.

Test plan

• programa-unit and programa-ci build-for-testing succeed locally; both new files compile.
• Unit test shards pass in CI, including MarkdownFindRegressionTests.
• test-e2e.yml with test_filter=CloseWorkspacesConfirmDialogUITests passes on this branch.