Fix import error: rename tui.py to tui_app.py to avoid package naming conflict

Resolved naming conflict between trace/tui.py (file) and trace/tui/ (package).
Python prioritizes packages over modules with the same name, causing import failures.

Changes:
- Renamed trace/tui.py to trace/tui_app.py
- Updated trace/cli.py to import from tui_app
- Updated trace/tui/__init__.py to re-export from tui_app for backward compatibility

This allows both direct imports (from trace.tui_app) and package imports (from trace.tui)
to work correctly, maintaining backward compatibility while supporting the new modular structure.

trace/cli.py

@@ -163,7 +163,7 @@ def main():
 
     # Launch TUI (with optional direct navigation to active context)
     try:
-        from .tui import run_tui
+        from .tui_app import run_tui
         run_tui(open_active=args.open)
     except ImportError as e:
         print(f"Error launching TUI: {e}")

trace/tui/__init__.py

@@ -1,6 +1,7 @@
 """TUI (Text User Interface) package for trace application"""
 
-# Import from the main tui module for backward compatibility
-# The tui.py file contains the main TUI class and run_tui function
+# Import from the main tui_app module for backward compatibility
+# The tui_app.py file contains the main TUI class and run_tui function
+from ..tui_app import run_tui, TUI
 
-__all__ = []
+__all__ = ['run_tui', 'TUI']