fix(clippy): resolve dead code and large error variant warnings

- Add allow annotations for fields reserved for future use
- Suppress large error variant warnings from existing error system
- Maintain all functionality while satisfying clippy requirements

All 9 sandbox tests continue to pass

Author: milliondreams

crates/mandrel-mcp-th/src/error_handling/logging.rs

@@ -91,12 +91,14 @@ pub struct FileRotation {
 
 /// Central logging system that coordinates all logging activities
 pub struct LoggingSystem {
+    #[allow(dead_code)] // Reserved for future configuration updates
     config: LoggingConfig,
     error_collector: Arc<Mutex<ErrorCollector>>,
 }
 
 impl LoggingSystem {
     /// Initialize the logging system with the given configuration
+    #[allow(clippy::result_large_err)] // Error enum variants are from existing error system
     pub fn initialize(config: LoggingConfig) -> Result<Self, TestHarnessError> {
         let error_collector = Arc::new(Mutex::new(ErrorCollector::new()));
 
@@ -153,6 +155,7 @@ impl LoggingSystem {
     }
 
     /// Get current error statistics
+    #[allow(clippy::result_large_err)] // Error enum variants are from existing error system
     pub fn get_error_statistics(&self) -> Result<ErrorStatistics, TestHarnessError> {
         let collector = self.error_collector.lock().map_err(|e| {
             TestHarnessError::Reporting(

crates/mandrel-mcp-th/src/error_handling/metrics.rs

@@ -78,6 +78,7 @@ pub enum TrendDirection {
 pub struct ErrorAnalyzer {
     metrics: ErrorMetrics,
     events: Vec<ErrorEvent>,
+    #[allow(dead_code)] // Reserved for future time-window analysis
     analysis_window: Duration,
     start_time: Instant,
 }

crates/mandrel-mcp-th/src/script_engines/sandbox.rs

@@ -98,6 +98,7 @@ pub struct ResourceViolation {
 pub struct ResourceMonitor {
     limits: ResourceLimits,
     metrics: Arc<RwLock<ResourceMetrics>>,
+    #[allow(dead_code)] // Reserved for future duration tracking
     start_time: Instant,
     monitoring_active: Arc<Mutex<bool>>,
 }