[FEATURE] VS Code extension: draw function-hook mod UI (AbovePrompt band, Pane)

Summary

Mods written as function-hook plugins draw nothing in the VS Code extension's chat panel. Please let the extension attach as a render surface so ui.render for AbovePrompt (and Pane) shows up there, as it does in the terminal and Desktop.

Environment

• Claude Code 2.1.288, VS Code extension anthropic.claude-code-2.1.288-win32-x64, Windows 11
• Mod loaded via hot reload (dev-mods folder), and separately via --plugin-dir

What happens

A mod that renders a two-row band on ui.render { component: 'AbovePrompt' } works in the terminal CLI. In the VS Code chat panel:

• $.session.surfaces() returns []
• $.ui.open({ id, title }) resolves { isPlaced: true }, but no pane appears anywhere
• AbovePrompt is documented as raised on terminal and desktop only, so the band never renders
• Slash commands registered by the mod work, and their { text } replies display

Expected

The vscode surface, which already exists in Elements and RenderSurface, gets attached in the chat panel and draws at least AbovePrompt and Pane. Alternatively, ui.open should return isPlaced: false with a reason when no surface can draw the pane.

Use case

Showing the 5-hour rate-limit usage above the input field, using a mod built on session.measure. The panel already shows the context-window fill (the ring in the input bar) but not the rate-limit windows. Many people use the VS Code panel as their main interface, and today they can't see their 5-hour usage while working there.