fix(smart v0.1.17): smart_status optionnel + AmbientCapabilities CAP_SYS_ADMIN

- SmartJson.smart_status devient Option<SmartStatus> avec #[serde(default)]
  → parsing non-bloquant si le champ est absent (ex: NVME_IOCTL_ADMIN_CMD échoue)
- Service: suppression NoNewPrivileges, ajout AmbientCapabilities=CAP_SYS_ADMIN
  → smartctl hérite la capability via execve (kernel ≥ 5.2)
- Nettoyage logs debug (suppression dump JSON brut)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

agent/src/metrics/smart.rs

@@ -2,7 +2,8 @@ use serde::Deserialize;
 
 #[derive(Deserialize)]
 struct SmartJson {
-    smart_status: SmartStatus,
+    #[serde(default)]
+    smart_status: Option<SmartStatus>,
     temperature: Option<SmartTemp>,
     ata_smart_attributes: Option<SmartAttrs>,
     nvme_smart_health_information_log: Option<NvmeHealth>,
@@ -78,7 +79,7 @@ pub fn parse_json(json: &str) -> Result<crate::payload::SmartMetrics, serde_json
 
     Ok(crate::payload::SmartMetrics {
         device: String::new(),
-        passed: s.smart_status.passed,
+        passed: s.smart_status.as_ref().map(|s| s.passed).unwrap_or(false),
         temperature,
         reallocated_sectors: reallocated,
         power_on_hours: power_hours,
@@ -125,12 +126,9 @@ pub fn collect() -> Option<Vec<crate::payload::SmartMetrics>> {
             Ok(o) => o,
             Err(e) => { eprintln!("[smart] erreur exec smartctl {}: {}", dev, e); continue }
         };
-        eprintln!("[smart] smartctl {} → exit={}, stdout={} octets, stderr={} octets",
-            dev, output.status, output.stdout.len(), output.stderr.len());
         let json = String::from_utf8_lossy(&output.stdout);
         match parse_json(&json) {
             Ok(metrics) => {
-                eprintln!("[smart] {} parsé OK (passed={})", dev, metrics.passed);
                 results.push(crate::payload::SmartMetrics {
                     device: dev.trim_start_matches("/dev/").to_string(),
                     ..metrics
@@ -138,9 +136,6 @@ pub fn collect() -> Option<Vec<crate::payload::SmartMetrics>> {
             }
             Err(e) => {
                 eprintln!("[smart] {} parse JSON échoué: {}", dev, e);
-                eprintln!("[smart] --- JSON BRUT BEGIN ({} octets) ---", json.len());
-                eprintln!("{}", &*json);
-                eprintln!("[smart] --- JSON BRUT END ---");
             }
         }
     }