build: wire JaCoCo coverage reports + spotless cleanup

Apply the jacoco plugin to every java-library subproject so every test
task is finalized by jacocoTestReport with XML and HTML output. Coverage
threshold enforcement (#33 80% target) is left as follow-up — the
plumbing is in place so further test additions raise the headline number
incrementally.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nficano

arcp-client/src/main/java/dev/arcp/client/ArcpClient.java

@@ -99,6 +99,7 @@ static EnumSet<Feature> safeFeatureCopy(Set<Feature> features) {
       new ConcurrentHashMap<>();
   private final ConcurrentHashMap<JobId, ExecutorService> liveExecutors = new ConcurrentHashMap<>();
   private final boolean ownedScheduler;
+
   // Reserved for future use by tests asserting FIFO insertion order of pending submits.
   @SuppressWarnings("unused")
   private final ConcurrentLinkedDeque<MessageId> pendingSubmitOrder = new ConcurrentLinkedDeque<>();
@@ -127,8 +128,7 @@ private ArcpClient(Builder b) {
       this.scheduler =
           Executors.newScheduledThreadPool(
               1,
-              r ->
-                  Thread.ofPlatform().name("arcp-client-scheduler", 0).daemon(true).unstarted(r));
+              r -> Thread.ofPlatform().name("arcp-client-scheduler", 0).daemon(true).unstarted(r));
       this.ownedScheduler = true;
     }
     this.resumeToken = b.resumeToken;
@@ -256,13 +256,7 @@ public void unsubscribe(JobId jobId) {
     }
     if (!closed) {
       try {
-        send(
-            Message.Type.JOB_UNSUBSCRIBE,
-            new JobUnsubscribe(jobId),
-            sessionId,
-            null,
-            jobId,
-            null);
+        send(Message.Type.JOB_UNSUBSCRIBE, new JobUnsubscribe(jobId), sessionId, null, jobId, null);
       } catch (RuntimeException ignored) {
         // best-effort
       }
@@ -379,7 +373,8 @@ private void failAll(Throwable cause) {
       o.events.close();
     }
     outstanding.clear();
-    for (java.util.Map.Entry<MessageId, CompletableFuture<SessionJobs>> e : listRequests.entrySet()) {
+    for (java.util.Map.Entry<MessageId, CompletableFuture<SessionJobs>> e :
+        listRequests.entrySet()) {
       if (!e.getValue().isDone()) {
         e.getValue().completeExceptionally(cause);
       }

arcp-core/src/main/java/dev/arcp/core/wire/ArcpMapper.java

@@ -36,9 +36,8 @@ public static ObjectMapper create() {
   /**
    * Shared mapper for hot-path use.
    *
-   * Treat this instance as read-only. Reconfiguring the shared mapper can
-   * affect unrelated callers because the same ObjectMapper is reused across
-   * the SDK.
+   * <p>Treat this instance as read-only. Reconfiguring the shared mapper can affect unrelated
+   * callers because the same ObjectMapper is reused across the SDK.
    */
   public static ObjectMapper shared() {
     return SHARED;

arcp-runtime/src/main/java/dev/arcp/runtime/ArcpRuntime.java

@@ -84,11 +84,7 @@ private ArcpRuntime(Builder b) {
       this.scheduler =
           Executors.newScheduledThreadPool(
               1,
-              r ->
-                  Thread.ofPlatform()
-                      .name("arcp-runtime-scheduler", 0)
-                      .daemon(true)
-                      .unstarted(r));
+              r -> Thread.ofPlatform().name("arcp-runtime-scheduler", 0).daemon(true).unstarted(r));
       this.ownedScheduler = true;
     }
     this.runtimeName = b.runtimeName;

arcp-runtime/src/main/java/dev/arcp/runtime/credentials/CredentialBinding.java

@@ -91,8 +91,7 @@ private void revoke(IssuedCredential credential) {
       } catch (CompletionException e) {
         Throwable cause = e.getCause() != null ? e.getCause() : e;
         if (attempt == MAX_REVOKE_ATTEMPTS) {
-          log.warn(
-              "credential revoke failed after {} attempts for {}", attempt, id, cause);
+          log.warn("credential revoke failed after {} attempts for {}", attempt, id, cause);
           store.markRevocationFailed(id, cause);
           return;
         }

arcp-runtime/src/main/java/dev/arcp/runtime/idempotency/IdempotencyStore.java

@@ -92,8 +92,8 @@ public boolean matchesPayload(Principal principal, String idempotencyKey, String
 
   /**
    * Evict entries older than {@code ttl}. Exposed for deterministic test control; the scheduled
-   * background task invokes this method automatically when a scheduler was supplied at
-   * construction time.
+   * background task invokes this method automatically when a scheduler was supplied at construction
+   * time.
    */
   public void prune() {
     Instant now = clock.instant();

arcp-runtime/src/main/java/dev/arcp/runtime/session/SessionLoop.java

@@ -798,7 +798,8 @@ private void handleSubscribe(JobSubscribe sub) {
       return;
     }
     boolean alreadySubscribed =
-        rec.subscribers().stream().anyMatch(s -> s.session() == this && s.jobId().equals(rec.jobId()));
+        rec.subscribers().stream()
+            .anyMatch(s -> s.session() == this && s.jobId().equals(rec.jobId()));
     if (!alreadySubscribed) {
       rec.addSubscriber(new JobRecord.Subscriber(this, rec.jobId()));
     }

build.gradle.kts

@@ -13,6 +13,7 @@ allprojects {
 
 subprojects {
     plugins.withId("java-library") {
+        apply(plugin = "jacoco")
         extensions.configure<JavaPluginExtension> {
             toolchain {
                 languageVersion.set(JavaLanguageVersion.of(21))
@@ -34,6 +35,14 @@ subprojects {
         }
         tasks.withType<Test>().configureEach {
             useJUnitPlatform()
+            finalizedBy("jacocoTestReport")
+        }
+        tasks.withType<JacocoReport>().configureEach {
+            dependsOn("test")
+            reports {
+                xml.required.set(true)
+                html.required.set(true)
+            }
         }
         tasks.withType<Javadoc>().configureEach {
             (options as? StandardJavadocDocletOptions)?.apply {