Adds a new mixin with programmatic engagement methods:
- like(tweetId) - FavoriteTweet
- unlike(tweetId) - UnfavoriteTweet
- retweet(tweetId) - CreateRetweet
- unretweet(tweetId) - DeleteRetweet
- bookmark(tweetId) - CreateBookmark
Implementation follows existing mixin patterns with:
- Shared performEngagementMutation() helper
- 404 retry with query ID refresh
- Returns BookmarkMutationResult for consistency
Also adds query IDs for the new operations to constants and
the update-query-ids script.
Includes 9 tests covering success cases, error handling, and retry logic.
