fix(ai): preserve Responses item IDs - #40943

Summary

• preserve response item IDs for reasoning, assistant messages, function calls, and function outputs regardless of store
• replay complete provider-hosted output items instead of synthesizing item_reference inputs
• make OpenAI, Azure, and Open Responses use the same client-managed history shape for store: true and store: false
• default generic Open Responses routes to store: false, matching the OpenAI/Azure native routes
• retain lifecycle metadata through terminal events so IDs, phases, and encrypted reasoning survive durable replay
• generate stable, prefixed fallback IDs for client-created or invalid items without collisions from sanitization/truncation

This aligns native Responses history with the OpenAI SDK manual-history guidance and Codex commit 4a443994bd, where store controls server persistence rather than outbound item-ID serialization.

Testing

• bun typecheck in packages/ai
• OpenAI Responses and Open Responses-compatible protocol tests: 81 passed
• affected recorded OpenAI Responses, hosted-image, and PDF continuation tests passed
• bun typecheck in packages/core
• core session message and tool-event persistence tests: 28 passed
• full AI suite: all affected tests passed; three unrelated latest-v2 failures remain from stale Azure Chat/OpenRouter fixture expectations