feat: add rate limiting, retry with backoff, and max count cap

- Add configurable request delay between paginated API calls (default 1.5s)
- Add retry with exponential backoff on HTTP 429 and Twitter error code 88
- Add hard max count cap (default 200, absolute ceiling 500)
- Add rateLimit config section with requestDelay, maxRetries, retryBaseDelay, maxCount
- Add normalization tests for rateLimit config

tests/test_cli.py

@@ -12,7 +12,7 @@ def test_cli_user_command_works_with_client_factory(monkeypatch) -> None:
         def fetch_user(self, screen_name: str) -> UserProfile:
             return UserProfile(id="1", name="Alice", screen_name=screen_name)
 
-    monkeypatch.setattr("twitter_cli.cli._get_client", lambda: FakeClient())
+    monkeypatch.setattr("twitter_cli.cli._get_client", lambda config=None: FakeClient())
     runner = CliRunner()
     result = runner.invoke(cli, ["user", "alice"])
     assert result.exit_code == 0

tests/test_config_normalization.py

@@ -33,3 +33,30 @@ def test_filter_normalization_for_invalid_values(tmp_path: Path) -> None:
     assert config["filter"]["lang"] == []
     assert config["filter"]["weights"]["likes"] == 1.0
     assert config["filter"]["weights"]["retweets"] == 4.0
+    # rateLimit should get defaults since it wasn't in the yaml
+    assert config["rateLimit"]["requestDelay"] == 1.5
+    assert config["rateLimit"]["maxRetries"] == 3
+    assert config["rateLimit"]["retryBaseDelay"] == 5.0
+    assert config["rateLimit"]["maxCount"] == 200
+
+
+def test_rate_limit_normalization(tmp_path: Path) -> None:
+    config_file = tmp_path / "config.yaml"
+    config_file.write_text(
+        "\n".join(
+            [
+                "rateLimit:",
+                "  requestDelay: -2",
+                "  maxRetries: bad",
+                "  retryBaseDelay: 0.1",
+                "  maxCount: 0",
+            ]
+        ),
+        encoding="utf-8",
+    )
+
+    config = load_config(str(config_file))
+    assert config["rateLimit"]["requestDelay"] == 0.0  # clamped to >= 0
+    assert config["rateLimit"]["maxRetries"] == 3  # fallback to default
+    assert config["rateLimit"]["retryBaseDelay"] == 1.0  # clamped to >= 1.0
+    assert config["rateLimit"]["maxCount"] == 1  # clamped to >= 1