Extract visibility metadata from TweetWithVisibilityResults wrapper
before unwrapping. Adds is_subscriber_only field to Tweet model,
with full serialization roundtrip and test coverage.
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Twitter long tweets (>280 chars) store full text in
note_tweet.note_tweet_results.result.text rather than legacy.full_text.
The parser now prioritizes note_tweet text when available.