fix(ai): replay responses history independently of storage - #45050

Summary

• treat Responses store strictly as provider persistence policy instead of changing conversation-history lowering or reasoning lifecycle
• model shared hosted items with explicit schemas for web_search_call, file_search_call, code_interpreter_call, and mcp_call; reject malformed known payloads and unknown tool discriminators
• compose OpenAI-only computer/preview/image items and xAI-only X-search/image items in their respective protocol request schemas instead of accepting arbitrary *_call values in the shared baseline
• replay same-provider JSON hosted results through schema-backed provider extensions while preserving generated images, hosted errors, malformed items, and foreign-provider results as portable content
• always replay complete reasoning items and preserve encrypted reasoning metadata independently of storage; remove synthetic item_reference generation
• refresh the hosted image-generation/edit cassette against the live OpenAI API

Supersedes the narrower native hosted-tool replay in #45038.

Before and after

Previously the shared Responses schema accepted essentially any object whose type ended in _call, including provider-private or invented tool types, and replay checked the suffix manually. Stored reasoning and hosted results were also rewritten into references:

[
  { "type": "item_reference", "id": "rs_1" },
  { "type": "item_reference", "id": "ws_1" }
]

Now the provider-neutral schema accepts only its explicitly modeled hosted items, OpenAI and xAI compose their own private extensions, and both storage modes preserve valid provider-native history:

[
  {
    "type": "reasoning",
    "id": "rs_1",
    "summary": [{ "type": "summary_text", "text": "Checked the previous diff." }],
    "encrypted_content": "encrypted-state"
  },
  { "type": "web_search_call", "id": "ws_1", "status": "completed" }
]

An xAI x_search_call remains valid only through xAI protocol composition; OpenAI computer_call remains valid only through OpenAI protocol composition; unknown or malformed items fall back to portable message content. Generated images remain portable input_image content regardless of storage. Live OpenAI requests confirmed that native stateless web-search replay succeeds, while native image-item replay fails because hosted images are not persisted.

Verification

• Live OpenAI hosted web-search native replay with store: false
• Focused live recording of the OpenAI hosted image-generation/edit scenario
• bun test test/partial-json.test.ts test/tool-stream.test.ts test/provider/openai-responses.test.ts test/provider/openai-compatible-responses.test.ts test/provider/openai-responses-images.recorded.test.ts test/provider/openai-responses-websocket.recorded.test.ts test/provider/openai-chat.test.ts test/provider/anthropic-messages.test.ts test/provider/bedrock-converse.test.ts test/provider/xai-responses.test.ts test/response.test.ts test/tool-runtime.test.ts --timeout 30000 --only-failures (373 passing)
• RECORDED_PREFIX=openai-responses bun test test/provider/golden.recorded.test.ts --timeout 30000 --only-failures
• RECORDED_PREFIX=pdf RECORDED_PROVIDER=xai bun test test/provider/pdf.recorded.test.ts --timeout 30000 --only-failures
• bun typecheck from packages/ai