feat(feature): add deterministic lifecycle arbitration

src/main/java/dev/hylfrd/farmhelper/feature/lifecycle/FeatureFailsafePolicy.java

@@ -0,0 +1,7 @@
+package dev.hylfrd.farmhelper.feature.lifecycle;
+
+/** Whether detector evidence is admissible while a feature is active. */
+public enum FeatureFailsafePolicy {
+    ALLOW_CHECKS,
+    SUPPRESS_CHECKS
+}

src/main/java/dev/hylfrd/farmhelper/feature/lifecycle/FeatureFailsafeSubmission.java

@@ -0,0 +1,42 @@
+package dev.hylfrd.farmhelper.feature.lifecycle;
+
+import dev.hylfrd.farmhelper.failsafe.FailsafeArbitrator;
+import dev.hylfrd.farmhelper.failsafe.FailsafeCandidate;
+
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+
+/** Explicit result of applying feature policy before domain failsafe arbitration. */
+public record FeatureFailsafeSubmission(
+        Status status,
+        FailsafeCandidate candidate,
+        List<FeatureId> suppressors,
+        Optional<FailsafeArbitrator.Submission> arbitration
+) {
+    public enum Status {
+        INACTIVE,
+        SUPPRESSED,
+        ARBITRATED
+    }
+
+    public FeatureFailsafeSubmission {
+        Objects.requireNonNull(status, "status");
+        Objects.requireNonNull(candidate, "candidate");
+        suppressors = List.copyOf(Objects.requireNonNull(suppressors, "suppressors"));
+        Objects.requireNonNull(arbitration, "arbitration");
+        if (status == Status.SUPPRESSED && suppressors.isEmpty()) {
+            throw new IllegalArgumentException("suppressed submission requires a suppressor");
+        }
+        if (status != Status.SUPPRESSED && !suppressors.isEmpty()) {
+            throw new IllegalArgumentException("only a suppressed submission may name suppressors");
+        }
+        if ((status == Status.ARBITRATED) != arbitration.isPresent()) {
+            throw new IllegalArgumentException("only an arbitrated submission may carry arbitration");
+        }
+    }
+
+    public boolean accepted() {
+        return arbitration.map(FailsafeArbitrator.Submission::accepted).orElse(false);
+    }
+}

src/main/java/dev/hylfrd/farmhelper/feature/lifecycle/FeatureId.java

@@ -0,0 +1,19 @@
+package dev.hylfrd.farmhelper.feature.lifecycle;
+
+import java.util.Objects;
+
+/** Stable, human-readable identity for one registered feature. */
+public record FeatureId(String value) {
+    public FeatureId {
+        Objects.requireNonNull(value, "value");
+        value = value.trim();
+        if (value.isEmpty()) {
+            throw new IllegalArgumentException("feature id must not be blank");
+        }
+    }
+
+    @Override
+    public String toString() {
+        return value;
+    }
+}