* feat(openai): add GPT-5.6 series support
* docs: refresh map for GPT-5.6
* fix(openai): preserve GPT-5.6 thinking metadata
* fix(codex): sync managed app server version
* fix(codex): sync managed app server version
* fix(openai): account for GPT-5.6 cache writes
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Co-authored-by: Peter Steinberger <steipete@golden-gate.local>
Refactor OpenAI provider identity so OpenAI remains the canonical provider for API-key and OAuth-backed flows while legacy openai-codex state is doctor/migration-only.
Keeps OpenAI Codex Responses as an API/transport class rather than a provider identity, moves auth aliases through providerAuthAliases, updates doctor repair sequencing for old auth/profile state, and refreshes tests/docs around the canonical OpenAI behavior.