Description

Add support for UsageMetaData, also includes a minor fix for prompt response text position.

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ( [x] ).
This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide ).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with /// ).
• The analyzer ( melos run analyze ) does not report any problems on my PR.
• I read and followed the Flutter Style Guide .
• I signed the CLA .
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change.
• No, this is not a breaking change.