VS Code extension: mods (plugin UI hooks) do not draw status line / toast / panes

In the Claude Code VS Code extension (2.1.289, macOS), a mod that loads and hot-reloads correctly draws nothing.

The mod API types list vscode as a render surface (RenderSurface = 'terminal' | 'desktop' | 'mobile' | 'vscode') and say a remote surface asks over the wire with ui_render. The extension's extension.js and webview/index.js have no handler for ui_render, nor for the calls behind $.ui.status and $.ui.toast. The only ui_* messages there are ui_copy, ui_prompt_fill, ui_prompt_read, ui_prompt_suggest and ui_read_selection.

Repro:

1. Load a mod that calls $.ui.status("test") from a prompt.submit hook, via hot reloading in the VS Code extension.
2. Send a prompt. The mod validates and loads, but no status line appears.
3. The same mod run in the terminal (claude --plugin-dir <mod>) shows the line under the prompt.

Request: support mod UI in the VS Code extension, at least $.ui.status and $.ui.toast, then ui.render slots such as AbovePrompt and Pane.

Use case: a status line showing the percentage used of the 5-hour and weekly rate-limit windows ($.session.usage().rateLimits).