test: add regression test for issue #212 (Anthropic web search :online error)

[robert-j-y]

Description

Adds a regression test for issue #212 ("Anthropic Model Error with Web Search :online Applied") to the e2e/issues/ directory.

Issue summary: Using anthropic/claude-sonnet-4.5:online with streamText threw AI_APICallError: Expected 'id' to be a string. The reporter noted that openai/gpt-4o:online worked correctly.

Test coverage:

• Streaming with anthropic/claude-sonnet-4.5:online using the exact code pattern from the original issue (prompt: parameter, textStream destructuring)
• Non-streaming (generateText) with the same model

Human Review Checklist

• Verify the test uses the exact model from issue Anthropic Model Error with Web Search :online Applied #212 (anthropic/claude-sonnet-4.5:online, not claude-3.5-sonnet)
• Verify the test matches the original issue's code pattern (uses prompt: parameter and textStream destructuring, not messages: array)
• Verify the test file follows the e2e/issues/ pattern established in PR test: add e2e/issues directory with issue #194 regression test #369
• Note: Tests depend on external API (anthropic/claude-sonnet-4.5:online) - may be slow or flaky if model is unavailable

Checklist

• I have run pnpm stylecheck and pnpm typecheck
• I have run pnpm test and all tests pass
• I have added tests for my changes (if applicable)
• I have updated documentation (if applicable)

Changeset

• I have run pnpm changeset to create a changeset file

Note: Empty changeset used since this is a test-only change that doesn't need a release.

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Link to Devin run: https://app.devin.ai/sessions/2ae2d68c4c464db78cc0191ddf33d9bc
Requested by: Robert Yeakel (@robert-j-y)