v0.2.0 — provider chat ports

Provider chat ports complete. All four providers now offer live, tool-use-capable chat behind the app-neutral interfaces, with the full live integration suite (simple-chat + tool-use, every provider) green as the Maestro cut-over acceptance gate.

Added since v0.1.0

• llms/providers/openai — OpenAI chat via the Responses API (structured message / function_call / function_call_output items; honors caller ToolChoice)
• llms/providers/google — Gemini chat via genai (stateless / concurrency-safe; real finish reason + usage)
• llms/providers/ollama — hand-rolled /api/chat client, no SDK dependency (avoids the ollama module's unfixed CVEs); raw done_reason + token usage
• Shared error classifier (apierr) — typed HTTP-status classification across anthropic + openai + google + ollama
• Live integration suite — build-tagged tests for all four providers, each with simple-chat and a full tool-use round trip; OS-aware make test-integration (macOS ad-hoc codesign path, Linux/CI plain go test); manual workflow_dispatch CI
• docs/MAESTRO_DIVERGENCES.md — living cut-over acceptance checklist

Deferred to v0.3 (not in this release)

Middleware: retry, timeout, circuit, metrics, validation. Shipped middleware remains ChainChat/ChainEmbeddings, token estimator, and ratelimit (from v0.1).

Pre-1.0: v0.x minor versions may break.