Fix config hash to show actual deployed nix store hash

- Replace git commit hash with nix store hash extraction
- Read from /run/current-system symlink target
- Extract first 8 characters of nix store hash: d8ivwiar
- Shows actual deployed configuration, not just source
- Enables proper rebuild completion detection
- Accurate deployment verification

agent/src/collectors/nixos.rs

@@ -63,27 +63,32 @@ impl NixOSCollector {
         Ok("unknown".to_string())
     }
 
-    /// Get configuration hash from cloned nixos-config git repository
+    /// Get configuration hash from deployed nix store system
     fn get_config_hash(&self) -> Result<String, Box<dyn std::error::Error>> {
-        // Get git hash from the cloned nixos-config directory
+        // Read the symlink target of /run/current-system to get nix store path
-        let config_path = "/var/lib/cm-dashboard/nixos-config";
+        let output = Command::new("readlink")
-        
+            .arg("/run/current-system")
-        let output = Command::new("git")
-            .args(&["log", "-1", "--format=%h"])
-            .current_dir(config_path)
             .output()?;
         
         if !output.status.success() {
-            return Err("git log command failed".into());
+            return Err("readlink command failed".into());
         }
         
-        let hash = String::from_utf8_lossy(&output.stdout).trim().to_string();
+        let binding = String::from_utf8_lossy(&output.stdout);
+        let store_path = binding.trim();
         
-        if hash.is_empty() {
+        // Extract hash from nix store path
-            return Err("Empty git hash output".into());
+        // Format: /nix/store/HASH-nixos-system-HOSTNAME-VERSION
+        if let Some(hash_part) = store_path.strip_prefix("/nix/store/") {
+            if let Some(hash) = hash_part.split('-').next() {
+                if hash.len() >= 8 {
+                    // Return first 8 characters of nix store hash
+                    return Ok(hash[..8].to_string());
+                }
+            }
         }
         
-        Ok(hash)
+        Err("Could not extract hash from nix store path".into())
     }
 
     /// Get currently active users
@@ -178,7 +183,7 @@ impl Collector for NixOSCollector {
                     name: "system_config_hash".to_string(),
                     value: MetricValue::String(hash),
                     unit: None,
-                    description: Some("NixOS configuration git hash".to_string()),
+                    description: Some("NixOS deployed configuration hash".to_string()),
                     status: Status::Ok,
                     timestamp,
                 });
@@ -189,7 +194,7 @@ impl Collector for NixOSCollector {
                     name: "system_config_hash".to_string(),
                     value: MetricValue::String("unknown".to_string()),
                     unit: None,
-                    description: Some("Config hash (failed to detect)".to_string()),
+                    description: Some("Deployed config hash (failed to detect)".to_string()),
                     status: Status::Unknown,
                     timestamp,
                 });