Clean up UI code and improve agent hash display

- Remove unused imports and debug logging
- Change agent display from 'Agent Hash: full' to 'Agent: short8'
- Fix unused variable warnings

dashboard/src/ui/widgets/system.rs

@@ -1,9 +1,8 @@
 use cm_dashboard_shared::{Metric, MetricValue, Status};
 use ratatui::{
     layout::Rect,
-    style::Style,
     text::{Line, Span, Text},
-    widgets::{Block, Borders, Paragraph},
+    widgets::Paragraph,
     Frame,
 };
 
@@ -299,10 +298,6 @@ impl Widget for SystemWidget {
         self.has_data = !metrics.is_empty();
 
         for metric in metrics {
-            // Debug logging for NixOS metrics
-            if metric.name.starts_with("system_") {
-                tracing::debug!("SystemWidget received metric: {} = {:?}", metric.name, metric.value);
-            }
             match metric.name.as_str() {
                 // NixOS metrics
                 "system_nixos_build" => {
@@ -405,8 +400,13 @@ impl Widget for SystemWidget {
         ]));
 
         let agent_hash_text = self.agent_hash.as_deref().unwrap_or("unknown");
+        let short_hash = if agent_hash_text.len() > 8 && agent_hash_text != "unknown" {
+            &agent_hash_text[..8]
+        } else {
+            agent_hash_text
+        };
         lines.push(Line::from(vec![
-            Span::styled(format!("Agent Hash: {}", agent_hash_text), Typography::secondary())
+            Span::styled(format!("Agent: {}", short_hash), Typography::secondary())
         ]));
 
         // CPU section