chat: askQuestions option descriptions take too much vertical space in the question carousel

## Issue Type

Enhancement / UX improvement

## Component

Chat → question carousel (rendered by the built-in `vscode/askQuestions` tool, `ChatQuestionCarouselPart`).

## Problem

When an agent asks clarifying questions via `vscode/askQuestions`, each option that carries a description is rendered as **two lines** — a title span (`.chat-question-list-label-title`) and a description span (`.chat-question-list-label-desc`) — inside a card whose outer container is capped at `max-height: min(420px, 45vh)`. For 3–4 options with typical descriptions, the card occupies most of the chat panel and hides the agent's own prior output that the user is reading when the question appears.

## Expected behavior

CLI agents like Codex present the same data more efficiently:

- The option list shows only the short titles (one line each).
- The description appears on demand, as a hover tooltip on the row the user is actually looking at.

This keeps the full context reachable while letting the user scan the option set at a glance.

## Suggested change

`src/vs/workbench/contrib/chat/browser/widget/chatContentParts/media/chatQuestionCarousel.css`:

1. Hide the description span (`.chat-question-list-label-desc { display: none; }`). The DOM element stays in place — assistive tech and any test assertions still see it; only the visual layout collapses to a single line per option.
2. Reduce the outer `max-height` from `min(420px, 45vh)` to `min(300px, 35vh)` as a secondary safety net.

The hover tooltip is already wired: `renderSingleSelect` / `renderMultiSelect` call `_hoverService.setupDelayedHover(listItem, { content: option.label, position: HoverPosition.BELOW })`, and `option.label` carries the full `"Title - Description"` string (the carousel only splits it into two DOM spans for display). So no TypeScript change is required.

## Impact

- Directly addresses the "card covers most of the window" complaint from users on long-description questions.
- Non-destructive: no data-model, no navigation, no answer-format change.
- One file, 2 lines.

## Environment

- VS Code Stable 1.107+ (chat.questionCarousel renderer shipped in `1.106`).
- Reproduced by triggering a 4-option `askQuestions` call from any agent (e.g., Architect) while signed in with Copilot.