Silence logfmt parse errors for non-logfmt logs

The logfmt stage tries to parse all logs, including JSON. When it fails,
it adds __error__ labels. Drop these labels since the logs are still
processed correctly (JSON parser already extracted fields).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

argocd/manifests/alloy-k8s/configmap.yaml

@@ -103,6 +103,7 @@ data:
       }
 
       // Try to parse logfmt logs (e.g., Loki, Prometheus, Go services)
+      // Silently skip lines that aren't valid logfmt
       stage.logfmt {
         mapping = {
           level     = "level",
@@ -112,6 +113,11 @@ data:
         }
       }
 
+      // Drop the logfmt error label if parsing failed (prevents noisy errors)
+      stage.label_drop {
+        values = ["__error__", "__error_details__"]
+      }
+
       // Extract labels from parsed data (works for both JSON and logfmt)
       stage.labels {
         values = {