feat: keep stream error toggle open by default

[uinstinct]

Description

Keep the error dialog toggle open by default.

resolves CON-4376 related to https://github.com/continuedev/continue/issues/8215

AI Code Review

• Team members only: AI review runs automatically when PR is opened or marked ready for review
• Team members can also trigger a review by commenting @continue-review

Checklist

• [] I've read the contributing guide
• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

Screen recording or screenshot

https://github.com/user-attachments/assets/fe3967a9-815f-4f4a-b5b8-d3e383cfe474

Tests

[ What tests were added or updated to ensure the changes work as expected? ]

---

Summary by cubic

Open the stream error details by default so error output is visible immediately and debugging is faster. Addresses CON-4376.

• New Features
  • Added a defaultOpen prop to ToggleDiv to control initial open state.
  • Enabled defaultOpen in StreamError for the “View error output” section.

^{Written for commit 3118030038adc291931a4599a094957789701f9a. Summary will update automatically on new commits.}