feat: add whoami, reply, quote, follow/unfollow commands and --compact mode

- whoami: fetch current authenticated user profile
- reply <id> <text>: standalone reply command
- quote <id> <text>: quote-tweet command
- follow/unfollow <handle>: follow/unfollow users
- --compact/-c: global flag for LLM-friendly minimal JSON output
- client.py: add fetch_me, quote_tweet, follow_user, unfollow_user
- serialization.py: add tweet_to_compact_dict, tweets_to_compact_json
- 7 new tests (82 total, all passing)

tests/test_cli.py

@@ -88,3 +88,109 @@ def test_cli_bookmark_alias_works(monkeypatch) -> None:
 
     assert result.exit_code == 0
     assert calls == ["123"]
+
+
+def test_cli_whoami_command(monkeypatch) -> None:
+    from twitter_cli.models import UserProfile
+
+    class FakeClient:
+        def fetch_me(self) -> UserProfile:
+            return UserProfile(id="42", name="Test User", screen_name="testuser")
+
+    monkeypatch.setattr("twitter_cli.cli._get_client", lambda config=None: FakeClient())
+    runner = CliRunner()
+
+    result = runner.invoke(cli, ["whoami"])
+    assert result.exit_code == 0
+
+    result_json = runner.invoke(cli, ["whoami", "--json"])
+    assert result_json.exit_code == 0
+    assert '"screenName": "testuser"' in result_json.output
+
+
+def test_cli_reply_command(monkeypatch) -> None:
+    calls = []
+
+    class FakeClient:
+        def create_tweet(self, text: str, reply_to_id=None) -> str:
+            calls.append({"text": text, "reply_to_id": reply_to_id})
+            return "999"
+
+    monkeypatch.setattr("twitter_cli.cli._get_client", lambda config=None: FakeClient())
+    runner = CliRunner()
+
+    result = runner.invoke(cli, ["reply", "12345", "Nice tweet!"])
+    assert result.exit_code == 0
+    assert calls[0]["reply_to_id"] == "12345"
+    assert calls[0]["text"] == "Nice tweet!"
+
+
+def test_cli_quote_command(monkeypatch) -> None:
+    calls = []
+
+    class FakeClient:
+        def quote_tweet(self, tweet_id: str, text: str) -> str:
+            calls.append({"tweet_id": tweet_id, "text": text})
+            return "888"
+
+    monkeypatch.setattr("twitter_cli.cli._get_client", lambda config=None: FakeClient())
+    runner = CliRunner()
+
+    result = runner.invoke(cli, ["quote", "12345", "Interesting!"])
+    assert result.exit_code == 0
+    assert calls[0]["tweet_id"] == "12345"
+    assert calls[0]["text"] == "Interesting!"
+
+
+def test_cli_follow_command(monkeypatch) -> None:
+    from twitter_cli.models import UserProfile
+    actions = []
+
+    class FakeClient:
+        def fetch_user(self, screen_name: str) -> UserProfile:
+            return UserProfile(id="42", name="Alice", screen_name=screen_name)
+
+        def follow_user(self, user_id: str) -> bool:
+            actions.append(("follow", user_id))
+            return True
+
+    monkeypatch.setattr("twitter_cli.cli._get_client", lambda config=None: FakeClient())
+    runner = CliRunner()
+
+    result = runner.invoke(cli, ["follow", "alice"])
+    assert result.exit_code == 0
+    assert actions == [("follow", "42")]
+
+
+def test_cli_unfollow_command(monkeypatch) -> None:
+    from twitter_cli.models import UserProfile
+    actions = []
+
+    class FakeClient:
+        def fetch_user(self, screen_name: str) -> UserProfile:
+            return UserProfile(id="42", name="Alice", screen_name=screen_name)
+
+        def unfollow_user(self, user_id: str) -> bool:
+            actions.append(("unfollow", user_id))
+            return True
+
+    monkeypatch.setattr("twitter_cli.cli._get_client", lambda config=None: FakeClient())
+    runner = CliRunner()
+
+    result = runner.invoke(cli, ["unfollow", "alice"])
+    assert result.exit_code == 0
+    assert actions == [("unfollow", "42")]
+
+
+def test_cli_compact_mode(tmp_path, tweet_factory) -> None:
+    json_path = tmp_path / "tweets.json"
+    json_path.write_text(tweets_to_json([tweet_factory("1")]), encoding="utf-8")
+
+    runner = CliRunner()
+    result = runner.invoke(cli, ["-c", "feed", "--input", str(json_path)])
+    assert result.exit_code == 0
+    # Compact output should have "author" field with @ prefix
+    assert '"@alice"' in result.output
+    # Compact output should NOT have full metrics keys
+    assert '"metrics"' not in result.output
+

tests/test_serialization.py

@@ -20,3 +20,32 @@ def test_tweets_json_roundtrip(tweet_factory) -> None:
 
     assert [tweet.id for tweet in restored] == ["1", "2"]
     assert restored[1].lang == "zh"
+
+
+def test_compact_serialization(tweet_factory) -> None:
+    from twitter_cli.serialization import tweet_to_compact_dict, tweets_to_compact_json
+    import json
+
+    tweet = tweet_factory(
+        "42",
+        created_at="Sat Mar 07 05:51:02 +0000 2026",
+        text="A" * 200,
+    )
+    compact = tweet_to_compact_dict(tweet)
+
+    assert compact["id"] == "42"
+    assert compact["author"] == "@alice"
+    assert compact["time"] == "Mar 07 05:51"
+    assert len(compact["text"]) <= 140
+    assert compact["text"].endswith("...")
+    assert compact["likes"] == 10
+    assert compact["rts"] == 2
+    # Should only have 6 keys
+    assert set(compact.keys()) == {"id", "author", "text", "likes", "rts", "time"}
+
+    # Test batch serialization
+    raw = tweets_to_compact_json([tweet])
+    parsed = json.loads(raw)
+    assert len(parsed) == 1
+    assert parsed[0]["author"] == "@alice"
+