feat(alerting): AGENT_STATE evaluator

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

cameleer-server-app/src/main/java/com/cameleer/server/app/alerting/eval/AgentStateEvaluator.java

@@ -0,0 +1,61 @@
+package com.cameleer.server.app.alerting.eval;
+
+import com.cameleer.server.core.agent.AgentInfo;
+import com.cameleer.server.core.agent.AgentRegistryService;
+import com.cameleer.server.core.agent.AgentState;
+import com.cameleer.server.core.alerting.AgentStateCondition;
+import com.cameleer.server.core.alerting.AlertRule;
+import com.cameleer.server.core.alerting.AlertScope;
+import com.cameleer.server.core.alerting.ConditionKind;
+import org.springframework.stereotype.Component;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+
+@Component
+public class AgentStateEvaluator implements ConditionEvaluator<AgentStateCondition> {
+
+    private final AgentRegistryService registry;
+
+    public AgentStateEvaluator(AgentRegistryService registry) {
+        this.registry = registry;
+    }
+
+    @Override
+    public ConditionKind kind() { return ConditionKind.AGENT_STATE; }
+
+    @Override
+    public EvalResult evaluate(AgentStateCondition c, AlertRule rule, EvalContext ctx) {
+        AgentState target = AgentState.valueOf(c.state());
+        Instant cutoff = ctx.now().minusSeconds(c.forSeconds());
+
+        List<AgentInfo> hits = registry.findAll().stream()
+                .filter(a -> matchesScope(a, c.scope()))
+                .filter(a -> a.state() == target)
+                .filter(a -> a.lastHeartbeat() != null && a.lastHeartbeat().isBefore(cutoff))
+                .toList();
+
+        if (hits.isEmpty()) return EvalResult.Clear.INSTANCE;
+
+        AgentInfo first = hits.get(0);
+        return new EvalResult.Firing(
+                (double) hits.size(), null,
+                Map.of(
+                        "agent", Map.of(
+                                "id",    first.instanceId(),
+                                "name",  first.displayName(),
+                                "state", first.state().name()
+                        ),
+                        "app", Map.of("slug", first.applicationId())
+                )
+        );
+    }
+
+    private static boolean matchesScope(AgentInfo a, AlertScope s) {
+        if (s == null) return true;
+        if (s.appSlug() != null && !s.appSlug().equals(a.applicationId())) return false;
+        if (s.agentId() != null && !s.agentId().equals(a.instanceId())) return false;
+        return true;
+    }
+}