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.

fastgpt_client/base_client.py

@@ -8,6 +8,15 @@ from typing import Any
 class BaseClientMixin:
     """Mixin class providing retry logic, validation, and logging for FastGPT clients."""
 
+    @staticmethod
+    def _normalize_base_url(base_url: str) -> str:
+        """Normalize FastGPT base URLs so '/api' is not duplicated by endpoint paths."""
+
+        normalized = str(base_url or "").strip().rstrip("/")
+        if normalized.endswith("/api"):
+            normalized = normalized[:-4]
+        return normalized
+
     def __init__(
         self,
         api_key: str,
@@ -28,7 +37,7 @@ class BaseClientMixin:
             enable_logging: Whether to enable request logging
         """
         self.api_key = api_key
-        self.base_url = base_url
+        self.base_url = self._normalize_base_url(base_url)
         self.timeout = timeout
         self.max_retries = max_retries
         self.retry_delay = retry_delay