[Requests and ideas] Add text-to-speech playback for chat and Markdown content

**Mood:** 😊
**Category:** Requests and ideas

## Problem / opportunity

Users should be able to listen to Copilot app content aloud, not only read it visually. This would be useful for longer chat responses, Markdown content in the side panel, accessibility needs, and multitasking workflows.

## Proposed solution

Add text-to-speech playback support in the GitHub Copilot app for both:

- The main chat window
- The side panel, including Markdown-rendered content

## Playback controls

The playback UI should include standard media controls:

- Play
- Pause
- Rewind
- Playback speed adjustment

## Model selection

Playback should use the existing voice and text capabilities already available to the app where possible. Users should be able to choose from the available text-to-speech or voice models for playback.

## User value

This would make Copilot app content easier to consume in more contexts, especially when reviewing longer generated responses, reading Markdown documentation, or using the app hands-free.

## Open questions

- Should playback work on selected text, an entire chat response, or the full side-panel document?
- Should model or voice selection be global, per-session, or per-playback?
- Should rewind jump by a fixed interval, sentence, paragraph, or message?
- Should playback speed settings persist across sessions?

---
| Field | Value |
| --- | --- |
| App version | 0.2.32 |
| OS | macOS 26.5.1 |
| Theme | Fox |
| Path | /chat |
| Tenure | Week 4 |

## Note

I am aware this can already be done through a custom extension, but it would be great to have this functionality available out of the box without having to generate a custom canvas extension.

该 issue 指出了 /chat 路径，但没有说明实现文件、测试或入口点。首先定位聊天和侧边面板的内容界面，并检查请求中提到的现有语音或文本功能。完成此项需要就内容选择范围、模型或语音选择、播放控制以及速度持久化达成一致，随后在所请求的两个界面中实现可正常工作的播放。

由索引模型根据 Issue 内容生成。