feat: add chat_tui example for FastGPT with Textual interface

- Introduced a new example script `chat_tui.py` that provides a full-screen Textual interface for interacting with FastGPT.
- Implemented streaming chat updates, workflow logging, and modal handling for interactive nodes.
- Enhanced FastGPT client with new streaming capabilities and structured event types for better interaction handling.
- Normalized base URL handling in the client to prevent duplicate `/api` paths.
- Added tests for streaming event parsing and interaction handling.

tests/test_chat_client.py

@@ -12,6 +12,14 @@ from fastgpt_client.exceptions import ValidationError
 class TestChatClientCreateChatCompletion:
     """Test suite for ChatClient.create_chat_completion method."""
 
+    def test_base_url_trailing_api_is_normalized(self, api_key):
+        """A base URL ending with /api should not produce /api/api/... requests."""
+
+        client = ChatClient(api_key, base_url="https://cloud.fastgpt.cn/api")
+
+        assert client.base_url == "https://cloud.fastgpt.cn"
+        assert str(client._client.base_url) == "https://cloud.fastgpt.cn"
+
     def test_create_chat_completion_basic(self, api_key, sample_chat_response):
         """Test basic chat completion creation."""
         client = ChatClient(api_key)