fix(console): preserve assistant content arrays - #41792

Issue for this PR

Closes #41766

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

OpenAI Responses API assistant messages may provide content as an array of output_text parts. fromOpenaiRequest only preserved string content, so array-form messages were forwarded without content and rejected.

This change joins the output_text parts into assistant content while preserving existing tool calls. It also adds regression coverage for multi-part assistant content.

How did you verify your code works?

• Added a regression test confirming that multiple output_text parts become hello world.
• Ran bun test test/providerRequest.test.ts from packages/console/app.
• Ran bun typecheck from packages/console/app.
• Passed the pre-push repository typecheck across 30 packages.

Screenshots / recordings

Not applicable; this is a non-UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR