refactor: dynamic UA matching, session reuse, score Optional, --output on all commands

- constants.py: sync_chrome_version() aligns UA/sec-ch-ua with impersonate target
- auth.py: reuse shared cffi session instead of creating duplicate
- filter.py: eliminate double weight building in score_tweet
- models.py: Tweet.score → Optional[float] for accurate display
- cli.py: add --output to search/likes/user-posts for consistency

twitter_cli/serialization.py

@@ -112,7 +112,7 @@ def tweet_from_dict(data: Dict[str, Any]) -> Tweet:
         lang=str(data.get("lang") or ""),
         retweeted_by=_optional_str(data.get("retweetedBy")),
         quoted_tweet=quoted_tweet,
-        score=float(data.get("score") or 0.0),
+        score=float(data["score"]) if data.get("score") is not None else None,
     )