Replace CPU frequency with C-state monitoring

- Changed CpuData.frequency_mhz to CpuData.cstate (String)
- Implemented collect_cstate() to read CPU idle depth from sysfs
- Finds deepest C-state with most accumulated time (C0-C10)
- Updated dashboard to display C-state instead of frequency
- More accurate indicator of CPU activity vs power management

Bump version to v0.1.208

Co-Authored-By: Claude <noreply@anthropic.com>

dashboard/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard"
-version = "0.1.206"
+version = "0.1.208"
 edition = "2021"
 
 [dependencies]

dashboard/src/ui/widgets/system.rs

@@ -26,7 +26,7 @@ pub struct SystemWidget {
     cpu_load_1min: Option<f32>,
     cpu_load_5min: Option<f32>,
     cpu_load_15min: Option<f32>,
-    cpu_frequency: Option<f32>,
+    cpu_cstate: Option<String>,
     cpu_status: Status,
     
     // Memory metrics
@@ -102,7 +102,7 @@ impl SystemWidget {
             cpu_load_1min: None,
             cpu_load_5min: None,
             cpu_load_15min: None,
-            cpu_frequency: None,
+            cpu_cstate: None,
             cpu_status: Status::Unknown,
             memory_usage_percent: None,
             memory_used_gb: None,
@@ -137,11 +137,11 @@ impl SystemWidget {
         }
     }
 
-    /// Format CPU frequency
-    fn format_cpu_frequency(&self) -> String {
-        match self.cpu_frequency {
-            Some(freq) => format!("{:.0} MHz", freq),
-            None => "— MHz".to_string(),
+    /// Format CPU C-state (idle depth)
+    fn format_cpu_cstate(&self) -> String {
+        match &self.cpu_cstate {
+            Some(cstate) => cstate.clone(),
+            None => "—".to_string(),
         }
     }
 
@@ -188,7 +188,7 @@ impl Widget for SystemWidget {
         self.cpu_load_1min = Some(cpu.load_1min);
         self.cpu_load_5min = Some(cpu.load_5min);
         self.cpu_load_15min = Some(cpu.load_15min);
-        self.cpu_frequency = Some(cpu.frequency_mhz);
+        self.cpu_cstate = Some(cpu.cstate.clone());
         self.cpu_status = Status::Ok;
 
         // Extract memory data directly
@@ -832,10 +832,10 @@ impl SystemWidget {
         );
         lines.push(Line::from(cpu_spans));
 
-        let freq_text = self.format_cpu_frequency();
+        let cstate_text = self.format_cpu_cstate();
         lines.push(Line::from(vec![
             Span::styled("  └─ ", Typography::tree()),
-            Span::styled(format!("Freq: {}", freq_text), Typography::secondary())
+            Span::styled(format!("C-state: {}", cstate_text), Typography::secondary())
         ]));
 
         // RAM section