Remove debug prints and unused code

- Remove all debug println statements
- Remove unused service_tracker module
- Remove unused struct fields and methods
- Remove empty placeholder files (cpu.rs, memory.rs, defaults.rs)
- Fix all compiler warnings
- Clean build with zero warnings

Version bump to 0.1.159

agent/src/collectors/nixos.rs

@@ -5,21 +5,18 @@ use std::process::Command;
 use tracing::debug;
 
 use super::{Collector, CollectorError};
-use crate::config::NixOSConfig;
 
 /// NixOS system information collector with structured data output
-/// 
+///
 /// This collector gathers NixOS-specific information like:
 /// - System generation/build information
 /// - Version information
 /// - Agent version from Nix store path
-pub struct NixOSCollector {
-    config: NixOSConfig,
-}
+pub struct NixOSCollector;
 
 impl NixOSCollector {
-    pub fn new(config: NixOSConfig) -> Self {
-        Self { config }
+    pub fn new(_config: crate::config::NixOSConfig) -> Self {
+        Self
     }
 
     /// Collect NixOS system information and populate AgentData