fix(opencode): update first ai provider batch

[rekram1-node]

Summary

• Update exactly three packages/opencode AI provider dependencies: @ai-sdk/cerebras, @ai-sdk/openai-compatible, and @openrouter/ai-sdk-provider.
• Pick up Cerebras reasoning/chat correctness fixes, OpenAI-compatible tool-message/streaming interoperability fixes, and OpenRouter duplicate streamed tool-call prevention.

Held Back

• Keep ai@6.0.168 unchanged as requested.
• Keep all remaining provider upgrade candidates out of this initial three-package batch.
• In particular, keep @ai-sdk/google@3.0.73 and @ai-sdk/google-vertex@4.0.128 because dev intentionally pins them before the known Google tool-call ID regression.

Validation

• bun test test/provider/transform.test.ts --timeout 30000 from packages/opencode
• bun typecheck from packages/opencode

[github-actions]

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