fix: file_search_call results missing document attributes/metadata (backport #4680)

[mergify]

What does this PR do?

Fixes a bug where chunk metadata attributes were not being passed through to file_search tool results in the Responses API. Document attributes are now properly included in OpenAIResponseOutputMessageFileSearchToolCallResults.attributes, allowing to cite sources and reference metadata.

Closes #4307

Test Plan

• Insert chunks with custom metadata using client.vector_io.insert()
• Query with file_search tool via client.responses.create()
• Verify metadata appears in result.attributes

---

This is an automatic backport of pull request #4680 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 28b92ba has failed:

On branch mergify/bp/release-0.3.x/pr-4680
Your branch is up to date with 'origin/release-0.3.x'.

You are currently cherry-picking commit 28b92bac.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   llama_stack/providers/inline/agents/meta_reference/responses/tool_executor.py
	both modified:   tests/unit/providers/agents/meta_reference/test_openai_responses.py

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally