Fix all clippy lints and pass CI checks

- Box large enum variants in EventData to reduce memory footprint
- Add Default trait implementations for types with new() methods
- Replace or_insert_with(Vec::new) with or_default()
- Convert vec init+push patterns to vec! macro
- Fix field reassignment with default initialization
- Convert match to if for simple equality checks
- Remove unused Backend type parameters from TUI draw functions
- Apply rustfmt formatting

All tests passing (24 total). Zero clippy warnings. Ready for CI/CD.

ghost-core/tests/detection_tests.rs

@@ -139,8 +139,10 @@ mod tests {
         let config = DetectionConfig::default();
         assert!(config.validate().is_ok());
 
-        let mut invalid_config = DetectionConfig::default();
-        invalid_config.confidence_threshold = 1.5; // Invalid
+        let mut invalid_config = DetectionConfig {
+            confidence_threshold: 1.5, // Invalid
+            ..Default::default()
+        };
         assert!(invalid_config.validate().is_err());
 
         invalid_config.confidence_threshold = -0.1; // Invalid
@@ -165,8 +167,10 @@ mod tests {
 
     #[test]
     fn test_engine_with_custom_config() {
-        let mut config = DetectionConfig::default();
-        config.hook_detection = false;
+        let config = DetectionConfig {
+            hook_detection: false,
+            ..Default::default()
+        };
 
         let mut engine =
             DetectionEngine::with_config(Some(config)).expect("Failed to create engine");