Add OpenAI chat completion wire mapping

[happylinks]

Summary

• validate the supported OpenAI Chat Completions request subset and reject unsupported fields
• translate system, developer, user, assistant, tool, and base64 image messages into pi-ai contexts
• serialize non-streaming completions and SSE chunks with tool-call deltas, finish reasons, usage, errors, and data: [DONE] termination
• keep reasoning content out of OpenAI assistant content

Testing

• bun run check
• 10 focused OpenAI wire tests, 25 package tests in total

Stack 2 of 2, based on #278.

Started by Michiel Westerbeek in this OS session

[open-session-os-tella-dev]

🤖 OS review · approve · confidence 5/5

Safe to merge. The PR validates the intended Chat Completions subset and consistently maps requests, non-streaming responses, streaming deltas, tool calls, usage, and errors to and from pi-ai. I found no merge-blocking correctness or compatibility issues.

💡 Labels: os-adversarial — deeper two-pass review · os-simplify — quality cleanup pass · os-auto-fix — fix anything outstanding and push until CI passes.
_{Reviewed 035c2cc · GPT-5.6 Sol · earlier reviews collapse above · open session}

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Project	Deployment	Actions	Updated
opensession	Ready	Preview	Sep 1, 2026 9:24pm UTC