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.

pyproject.toml

@@ -30,6 +30,10 @@ dependencies = [
 ]
 
 [project.optional-dependencies]
+examples = [
+    "python-dotenv>=1.0",
+    "textual>=8.0.0",
+]
 dev = [
     "pytest>=7.0",
     "pytest-cov>=4.0",