Per-message timestamp metadata injected by _apply_persist_user_message_override
leaks into the Chat Completions payload sent to the provider. Strict OpenAI-compatible
providers (e.g. Fireworks-backed endpoints like OpenCode Go 'glm-5.2', Mistral, Kimi)
reject this schema-foreign field with HTTP 400:
Extra inputs are not permitted, field: 'messages[0].timestamp'
The ChatCompletionsTransport.convert_messages already strips known internal-only
fields (tool_name, _-prefixed scaffolding keys, codex_reasoning_items, etc.) — add
timestamp to that list.
Closes#47868
4467c22c8f