docs: clarify tool search support and namespace guidance

[seratch]

This pull request updates the tool search documentation to align the JS SDK guides with the current Responses API behavior and the official tool search guide. It adds a new docs example for deferred tool loading, explains when to keep a deferred tool top-level versus grouping related tools with toolNamespace(), and documents that namespaced and top-level deferred tools can be mixed in the same request.

It also fills in the supporting guide coverage around tool search by:

• adding tool_search and toolSearchTool() to the main tools guide
• documenting the RunToolSearchCallItem / RunToolSearchOutputItem result surfaces
• documenting the tool_search_called / tool_search_output_created streaming events
• clarifying that deferred tool loading is Responses-only and should be used with GPT-5.4 and newer supported model releases

[changeset-bot]

⚠️ No Changeset found

Latest commit: 472f57c

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR