add structured error handling with thiserror

ghost-core/src/error.rs

@@ -0,0 +1,27 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum GhostError {
+    #[error("Process access denied (PID: {pid})")]
+    AccessDenied { pid: u32 },
+    
+    #[error("Process not found (PID: {pid})")]
+    ProcessNotFound { pid: u32 },
+    
+    #[error("Memory enumeration failed: {reason}")]
+    MemoryEnumeration { reason: String },
+    
+    #[error("Thread enumeration failed: {reason}")]
+    ThreadEnumeration { reason: String },
+    
+    #[error("Insufficient privileges for operation")]
+    InsufficientPrivileges,
+    
+    #[error("Windows API error: {message}")]
+    WindowsApi { message: String },
+    
+    #[error("Detection engine error: {message}")]
+    Detection { message: String },
+}
+
+pub type Result<T> = std::result::Result<T, GhostError>;

ghost-core/src/lib.rs

@@ -1,9 +1,11 @@
 pub mod detection;
+pub mod error;
 pub mod memory;
 pub mod process;
 pub mod thread;
 
 pub use detection::{DetectionEngine, DetectionResult, ThreatLevel};
+pub use error::{GhostError, Result};
 pub use memory::{MemoryProtection, MemoryRegion};
 pub use process::ProcessInfo;
 pub use thread::ThreadInfo;