fix: Fix plugin import path for installed plugins

The issue was that installed plugins (calculator, clock_widget, etc.)
could not import 'plugins.base_plugin' because the plugins package
wasn't properly in Python's module path when loading via
spec_from_file_location.

FIX:
1. Added project root to sys.path so 'plugins' package is findable
2. Added _ensure_plugins_package() method to preload plugins module
3. Modified discover_plugins() to try normal import first
4. Added proper error logging with traceback for debugging

This ensures installed plugins can properly import BasePlugin
from plugins.base_plugin as expected.

core/plugin_manager.py

@@ -29,12 +29,23 @@ class PluginManager:
         self.plugin_classes: Dict[str, Type[BasePlugin]] = {}
         self.config = self._load_config()
         
-        # Add plugin dirs to path
+        # Add plugin dirs and project root to path
+        # Project root needed for 'plugins.base_plugin' imports
+        project_root = Path(__file__).parent.parent.absolute()
+        if str(project_root) not in sys.path:
+            sys.path.insert(0, str(project_root))
+        
         for plugin_dir in self.PLUGIN_DIRS:
             path = Path(plugin_dir).absolute()
             if path.exists() and str(path) not in sys.path:
                 sys.path.insert(0, str(path))
         
+        # Ensure plugins package is loaded
+        try:
+            import plugins
+        except ImportError:
+            pass  # plugins package will be loaded when needed
+    
     def _load_config(self) -> dict:
         """Load plugin configuration."""
         config_path = Path("config/plugins.json")
@@ -90,6 +101,9 @@ class PluginManager:
         """Discover all available plugin classes with error handling."""
         discovered = []
         
+        # First, ensure plugins package is loaded
+        self._ensure_plugins_package()
+        
         for plugin_dir in self.PLUGIN_DIRS:
             base_path = Path(plugin_dir)
             if not base_path.exists():
@@ -110,12 +124,18 @@ class PluginManager:
                     continue
                 
                 try:
-                    # Load the plugin module
+                    # Load the plugin module using normal import
+                    # This ensures proper package resolution
                     module_name = f"{plugin_dir}.{item.name}.plugin"
                     
                     if module_name in sys.modules:
                         module = sys.modules[module_name]
                     else:
+                        # Try normal import first
+                        try:
+                            module = importlib.import_module(module_name)
+                        except ImportError:
+                            # Fall back to spec loading
                             spec = importlib.util.spec_from_file_location(
                                 module_name, plugin_file
                             )
@@ -137,10 +157,24 @@ class PluginManager:
                             
                 except Exception as e:
                     print(f"[PluginManager] Failed to discover {item.name}: {e}")
+                    import traceback
+                    traceback.print_exc()
                     continue
         
         return discovered
     
+    def _ensure_plugins_package(self):
+        """Ensure the plugins package is loaded in sys.modules."""
+        if 'plugins' not in sys.modules:
+            try:
+                import plugins
+            except ImportError:
+                # Create a minimal plugins module if it doesn't exist
+                import types
+                plugins_module = types.ModuleType('plugins')
+                plugins_module.__path__ = [str(Path('plugins').absolute())]
+                sys.modules['plugins'] = plugins_module
+    
     def load_plugin(self, plugin_class: Type[BasePlugin]) -> bool:
         """Instantiate and initialize a plugin with error handling."""
         try: