VS Code Speech cannot stop playback for long GitHub Copilot Chat responses

Does this issue occur when all extensions are disabled?: No

The issue requires GitHub Copilot Chat and VS Code Speech to reproduce. Disabling all extensions also disables the functionality being tested.

- VS Code Version: 1.129.1
- OS Version: Windows 11

Steps to Reproduce:

1. Open GitHub Copilot Chat.
2. Ask Copilot to generate a long response.
3. Click the speaker icon (🔊) to start speech playback.
4. While the response is being read aloud, click the stop icon (🔇) or press Esc.
5. Click the speaker icon (🔊) again.

Expected Result:

- Speech playback stops immediately when clicking the stop icon or pressing Esc.

Actual Result:

- The speaker icon changes back to its normal state, but speech playback continues.
- Pressing Esc has the same behavior.
- Clicking the speaker icon again starts another playback of the same message.
- Multiple playbacks of the same message can overlap and play simultaneously.
- Once this occurs, the original long playback cannot be stopped.

Additional Information:

- The issue occurs consistently with long Copilot Chat responses.
- Short responses worked correctly in my testing.
- I have not determined the exact length threshold at which the issue begins to occur.
- While a long response is stuck playing, short responses can still be started and stopped normally.
- Disabling the Claude Code extension did not change the behavior.
- The issue also occurs in a new Copilot Chat conversation.
- VS Code Speech version: 0.16.0
- GitHub Copilot Chat: Built-in extension (version 0.41)
- Speech language: Japanese (ja-JP)