fix(xai): emit tool-result for all provider-executed tools in Responses stream

[giulio-leone]

Summary

Fixes #13218 — Provider-executed tools (web_search, x_search, code_execution, etc.) in the xAI Responses API never emit tool-result when they complete, so UIs stay stuck on the 'in progress' state.

Root Cause

The doStream handler for response.output_item.done only emits tool-result for file_search_call but skips all other provider-executed tool types (web_search_call, x_search_call, code_interpreter_call, code_execution_call, view_image_call, view_x_video_call, custom_tool_call, mcp_call).

Similarly, the non-streaming doGenerate handler pushes tool-call but not tool-result for these tool types.

Fix

Extended both streaming and non-streaming handlers to emit tool-result for all provider-executed tool types, following the same pattern already used for file_search_call.

Streaming (doStream): Added tool-result emission on response.output_item.done events for all provider-executed tool types in the shared handler block.

Non-streaming (doGenerate): Added tool-result push after tool-call for all provider-executed tool types.

Testing

• Updated 6 existing doGenerate tests to verify tool-result is now emitted alongside tool-call for provider-executed tools
• Updated 5 snapshot tests to include the new tool-result entries
• Added 3 new streaming tests:
  • should stream web_search tool call and result — verifies tool-result on response.output_item.done
  • should stream code_execution tool call and result — verifies tool-result for code_execution_call
  • should stream custom_tool_call and result — verifies tool-result for custom_tool_call (used by x_search sub-tools)
• All 56 tests pass

[giulio-leone]

Friendly ping — CI is green, tests pass, rebased on latest main. Ready for review whenever convenient. Happy to address any feedback. 🙏