feat(messaging): 브로커 중립 메시징 플랫폼 24개 leaf 추가

messaging-superpowers-package 설계서/계획서 기반 구현.
registry를 19 → 43 leaf로 확장하고 src/messaging 아래 24개 leaf를 등록.

- core-api: M1 publish/consume + M2 batch·delayed·pause-resume
- policy/transport-spi: 재시도 결정, DLQ orchestration, admission control, lifecycle
- kafka·rabbit(Stable): contiguous commit, confirm/return 상관, 배치, 보안 설정
- pulsar·nats(Experimental): 기본 비활성, live 인증 없음을 코드로 기록
- outbox/inbox/claim-check: 트랜잭션 결합, lease, 무결성 검증
- admin: plan → approve → execute를 타입으로 강제
- 문서 9종, infra compose 7종, JMH 벤치마크 3종

검증: 아키텍처 게이트 3종 통과, 24개 leaf 전부 check 통과,
messaging 테스트 604개 통과/0 실패.

미완: 계획서가 요구한 실 브로커 IT 40개 중 7개만 작성.
Rabbit 13 / Outbox 6 / Inbox 4 / NATS·Pulsar·Share 5 / testkit 2 /
starter·admin 3, 그리고 TLS·ACL 2개가 남음.

src/build.gradle

@@ -431,7 +431,12 @@ configure(subprojects.findAll { it.childProjects.isEmpty() }) {
     }
 
     dependencies {
-        if (project.path in [':domain-core', ':application-core', ':shared-contract']) {
+        // The messaging platform leaves own a broker-neutral public contract. Keeping their test
+        // classpath on plain JUnit + AssertJ is what makes "messaging-core-api has no Spring
+        // dependency" verifiable rather than aspirational; leaves that genuinely need a Spring
+        // test context add it in their own build file.
+        if (project.path in [':domain-core', ':application-core', ':shared-contract'] ||
+                project.path.startsWith(':messaging:')) {
             testImplementation 'org.junit.jupiter:junit-jupiter'
             testImplementation 'org.assertj:assertj-core'
         } else {
@@ -444,6 +449,49 @@ configure(subprojects.findAll { it.childProjects.isEmpty() }) {
         errorprone 'com.google.errorprone:error_prone_core:2.49.0'            // D5 compile-time checker
     }
 
+    // The three messaging leaves that carry JMH benchmarks get a `jmh` source set. It is a source
+    // set rather than a plugin because the benchmarks are compiled and reviewed on every build but
+    // only *run* on demand: a benchmark that stops compiling is a defect, while a benchmark that
+    // runs in CI is a flaky test measuring the build agent.
+    if (project.path in [':messaging:messaging-kafka',
+                         ':messaging:messaging-rabbit',
+                         ':messaging:messaging-testkit']) {
+        sourceSets {
+            jmh {
+                compileClasspath += sourceSets.main.output + sourceSets.test.output
+                runtimeClasspath += sourceSets.main.output + sourceSets.test.output
+            }
+        }
+        configurations {
+            jmhImplementation.extendsFrom implementation, testImplementation
+            jmhRuntimeOnly.extendsFrom runtimeOnly, testRuntimeOnly
+        }
+        dependencies {
+            jmhImplementation 'org.openjdk.jmh:jmh-core:1.37'
+            jmhAnnotationProcessor 'org.openjdk.jmh:jmh-generator-annprocess:1.37'
+            // ErrorProne's -Werror would reject JMH's generated sources, which the platform does
+            // not own and cannot fix.
+            jmhAnnotationProcessor 'com.google.errorprone:error_prone_core:2.49.0'
+        }
+        tasks.named('compileJmhJava') {
+            options.errorprone.enabled = false
+            options.compilerArgs.removeAll { it == '-Werror' }
+        }
+        // JMH's annotation processor emits the generated harness into this source set, and its
+        // generated code trips DLS_DEAD_LOCAL_STORE by design (the dead stores are how it defeats
+        // dead-code elimination). Analysing code the platform neither wrote nor can fix would make
+        // the gate unactionable, so the jmh source set is excluded from the bug and style checks.
+        // The benchmarks themselves are still compiled, which is what catches a real breakage.
+        tasks.named('spotbugsJmh') { enabled = false }
+        tasks.named('checkstyleJmh') { enabled = false }
+        tasks.register('jmh', JavaExec) {
+            group = 'verification'
+            description = 'Runs the JMH benchmarks in this leaf.'
+            classpath = sourceSets.jmh.runtimeClasspath
+            mainClass = 'org.openjdk.jmh.Main'
+        }
+    }
+
     // feature-ci-quality-gates-contract §4 (D7) — the main release gate EXCLUDES the flaky
     // quarantine bucket so a quarantined test can never block merge. Quarantined tests carry
     // JUnit's built-in @Tag("quarantine"); they run separately via `quarantineTest` (non-blocking)