fix(ai): preserve unencrypted reasoning history - #45032

Summary

• stop dropping valid reasoning items from stateless Responses requests when encrypted_content is absent or null
• preserve reasoning IDs, visible summaries, and chronological conversation ordering regardless of encryption availability
• match Codex request construction, which replays reasoning items with encrypted_content: null while using store: false

Before and after

Given prior assistant reasoning without encrypted state:

{ "type": "reasoning", "id": "rs_1", "summary": [{ "type": "summary_text", "text": "Checked the previous diff." }], "encrypted_content": null }

Before: store: false removed the reasoning item entirely from the next request:

{ "store": false, "input": [
  { "role": "user", "content": [{ "type": "input_text", "text": "What changed?" }] },
  { "role": "assistant", "content": [{ "type": "output_text", "text": "The parser changed." }] }
] }

After: The reasoning item remains in its original conversation position:

{ "store": false, "input": [
  { "role": "user", "content": [{ "type": "input_text", "text": "What changed?" }] },
  { "type": "reasoning", "id": "rs_1", "summary": [{ "type": "summary_text", "text": "Checked the previous diff." }], "encrypted_content": null },
  { "role": "assistant", "content": [{ "type": "output_text", "text": "The parser changed." }] }
] }

Verification

• 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-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 (363 passing)
• RECORDED_PREFIX=openai-responses bun test test/provider/golden.recorded.test.ts --timeout 30000 --only-failures
• bun typecheck from packages/ai
• bunx prettier --check packages/ai/src/protocols/open-responses.ts packages/ai/test/provider/openai-responses.test.ts