Add Grok-native reasoning replay for Claude-sourced xAI Responses requests. Replay state is scoped by model and session, normalized to reasoning/function_call/custom_tool_call items, and injected with the same tool-call alignment semantics used by Codex. Include the minimal Grok encrypted_content validator needed on upstream/dev so replay cache entries cannot accept Codex/GPT, Gemini, or Claude signature shapes. Cache completed output items from HTTP, streaming, and WebSocket xAI responses. Cover two-turn Claude replay, tool_result continuity, valid Grok cache storage, and rejection of Codex-shaped encrypted_content.