Fix agent collector timing to prevent intermittent data gaps

Update last_collection timestamp even when collectors fail to prevent
immediate retry loops that cause data transmission gaps every 5 seconds.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

agent/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-agent"
-version = "0.1.133"
+version = "0.1.134"
 edition = "2021"
 
 [dependencies]

agent/src/metrics/mod.rs

@@ -232,6 +232,8 @@ impl MetricCollectionManager {
                     }
                     Err(e) => {
                         error!("Collector {} failed: {}", timed_collector.name, e);
+                        // Update last_collection time even on failure to prevent immediate retries
+                        timed_collector.last_collection = Some(now);
                     }
                 }
             }