Accessibility: Add verbosity setting, keybinding, and aria hints for question carousel terminal focus

[meganrogge]

Fixes #312423

Adds accessibility improvements to the askQuestions tool's question carousel when triggered by a terminal interaction:

• Verbosity setting — accessibility.verbosity.chatQuestionCarousel controls whether the carousel's aria label includes navigation hints
• Keybinding — Alt+T (workbench.action.chat.focusQuestionCarouselTerminal) to focus the terminal from the carousel, gated by a new chatQuestionCarouselHasTerminal context key so it only activates when a terminal is present
• Aria label hints — The Focus Terminal button includes the keybinding in its aria-label (e.g., "Focus Terminal (Alt+T)"), and when verbosity is enabled the carousel container's aria-label appends "Use Alt+T to focus the terminal."

[Copilot]

Pull request overview

This PR adds accessibility improvements to the chat question carousel when it’s triggered by a terminal interaction, including a new verbosity setting, an Alt+T keybinding to focus the related terminal, and richer aria-label hints.

Changes:

• Add accessibility.verbosity.chatQuestionCarousel to control whether navigation hints are appended to the carousel’s aria-label.
• Introduce workbench.action.chat.focusQuestionCarouselTerminal with Alt+T, gated by a new chatQuestionCarouselHasTerminal context key.
• Update the carousel UI to include keybinding-aware aria-label text and a focusTerminal() pathway.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/common/actions/chatContextKeys.ts	Adds chatQuestionCarouselHasTerminal context key to gate terminal-focus affordances.
src/vs/workbench/contrib/chat/browser/widget/input/chatInputPart.ts	Adds focusQuestionCarouselTerminal() plumbing from input part to the active carousel.
src/vs/workbench/contrib/chat/browser/widget/chatWidget.ts	Exposes focusQuestionCarouselTerminal() on ChatWidget for actions/keybindings.
src/vs/workbench/contrib/chat/browser/widget/chatContentParts/chatQuestionCarouselPart.ts	Adds verbosity-driven aria hints, keybinding label injection, and terminal-focus support plus context key wiring.
src/vs/workbench/contrib/chat/browser/chat.ts	Extends IChatWidget with focusQuestionCarouselTerminal().
src/vs/workbench/contrib/chat/browser/actions/chatActions.ts	Registers the new action + Alt+T keybinding with appropriate context gating.
src/vs/workbench/contrib/accessibility/browser/accessibilityConfiguration.ts	Adds the new verbosity setting to the accessibility configuration schema.

Copilot's findings

• Files reviewed: 7/7 changed files
• Comments generated: 2