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>

agent/src/collectors/cpu.rs

@@ -119,36 +119,40 @@ impl CpuCollector {
         utils::parse_u64(content.trim())
     }
 
-    /// Collect CPU frequency and populate AgentData
-    async fn collect_frequency(&self, agent_data: &mut AgentData) -> Result<(), CollectorError> {
-        // Try scaling frequency first (more accurate for current frequency)
-        if let Ok(freq) =
-            utils::read_proc_file("/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq")
-        {
-            if let Ok(freq_khz) = utils::parse_u64(freq.trim()) {
-                let freq_mhz = freq_khz as f32 / 1000.0;
-                agent_data.system.cpu.frequency_mhz = freq_mhz;
-                return Ok(());
-            }
-        }
+    /// Collect CPU C-state (idle depth) and populate AgentData
+    async fn collect_cstate(&self, agent_data: &mut AgentData) -> Result<(), CollectorError> {
+        // Read C-state usage from first CPU (representative of overall system)
+        // C-states indicate CPU idle depth: C1=light sleep, C6=deep sleep, C10=deepest
 
-        // Fallback: parse /proc/cpuinfo for base frequency
-        if let Ok(content) = utils::read_proc_file("/proc/cpuinfo") {
-            for line in content.lines() {
-                if line.starts_with("cpu MHz") {
-                    if let Some(freq_str) = line.split(':').nth(1) {
-                        if let Ok(freq_mhz) = utils::parse_f32(freq_str) {
-                            agent_data.system.cpu.frequency_mhz = freq_mhz;
-                            return Ok(());
+        let mut deepest_state = String::from("C0"); // Default to active
+        let mut max_time: u64 = 0;
+
+        // Check C-states from CPU0
+        for state_num in 0..=10 {
+            let time_path = format!("/sys/devices/system/cpu/cpu0/cpuidle/state{}/time", state_num);
+            let name_path = format!("/sys/devices/system/cpu/cpu0/cpuidle/state{}/name", state_num);
+
+            if let Ok(time_str) = utils::read_proc_file(&time_path) {
+                if let Ok(time) = utils::parse_u64(time_str.trim()) {
+                    if time > max_time {
+                        // This state has most accumulated time
+                        if let Ok(name) = utils::read_proc_file(&name_path) {
+                            let state_name = name.trim().to_string();
+                            // Skip POLL state (not real idle)
+                            if state_name != "POLL" {
+                                max_time = time;
+                                deepest_state = state_name;
+                            }
                         }
                     }
-                    break; // Only need first CPU entry
                 }
+            } else {
+                // No more states available
+                break;
             }
         }
 
-        debug!("CPU frequency not available");
-        // Leave frequency as 0.0 if not available
+        agent_data.system.cpu.cstate = deepest_state;
         Ok(())
     }
 }
@@ -165,8 +169,8 @@ impl Collector for CpuCollector {
         // Collect temperature (optional)
         self.collect_temperature(agent_data).await?;
 
-        // Collect frequency (optional)
-        self.collect_frequency(agent_data).await?;
+        // Collect C-state (CPU idle depth)
+        self.collect_cstate(agent_data).await?;
 
         let duration = start.elapsed();
         debug!("CPU collection completed in {:?}", duration);