Add backpressure stack for agentic coding quality gates

PostToolUse hooks run after every file edit:
- Backend: ./mvnw compile (Checkstyle Google Style + javac)
- Frontend: vue-tsc --noEmit + oxlint + ESLint

Stop hook runs test suites when source files changed, blocks the
agent on failure and re-engages it to fix the issue. Output is
filtered to [ERROR] lines only for context efficiency.

Static analysis: Checkstyle (validate phase), SpotBugs (verify phase),
ArchUnit (9 hexagonal architecture rules as JUnit tests).

Fail-fast: Surefire skipAfterFailureCount=1, Vitest bail=1.
Test log noise suppressed via logback-test.xml (WARN level),
redirectTestOutputToFile, and trimStackTrace.

Existing Java sources reformatted to Google Style (2-space indent,
import order, Javadoc on public types).

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

backend/pom.xml

@@ -33,10 +33,73 @@
             <scope>test</scope>
         </dependency>
 
+        <dependency>
+            <groupId>com.tngtech.archunit</groupId>
+            <artifactId>archunit-junit5</artifactId>
+            <version>1.4.1</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+                <version>3.6.0</version>
+                <dependencies>
+                    <dependency>
+                        <groupId>com.puppycrawl.tools</groupId>
+                        <artifactId>checkstyle</artifactId>
+                        <version>13.3.0</version>
+                    </dependency>
+                </dependencies>
+                <configuration>
+                    <configLocation>google_checks.xml</configLocation>
+                    <consoleOutput>true</consoleOutput>
+                    <failOnViolation>true</failOnViolation>
+                    <violationSeverity>warning</violationSeverity>
+                    <includeTestSourceDirectory>true</includeTestSourceDirectory>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>checkstyle-validate</id>
+                        <phase>validate</phase>
+                        <goals>
+                            <goal>check</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <configuration>
+                    <!-- Fail-fast: stop on first test failure -->
+                    <skipAfterFailureCount>1</skipAfterFailureCount>
+                    <!-- Context-efficient output for agent backpressure -->
+                    <trimStackTrace>true</trimStackTrace>
+                    <redirectTestOutputToFile>true</redirectTestOutputToFile>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>com.github.spotbugs</groupId>
+                <artifactId>spotbugs-maven-plugin</artifactId>
+                <version>4.9.8.2</version>
+                <configuration>
+                    <effort>Max</effort>
+                    <threshold>Low</threshold>
+                    <xmlOutput>true</xmlOutput>
+                    <failOnError>true</failOnError>
+                </configuration>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>check</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
             <plugin>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-maven-plugin</artifactId>

backend/src/main/java/de/fete/FeteApplication.java

@@ -3,10 +3,12 @@ package de.fete;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 
+/** Spring Boot entry point for the fete application. */
 @SpringBootApplication
 public class FeteApplication {
 
-    public static void main(String[] args) {
-        SpringApplication.run(FeteApplication.class, args);
-    }
+  /** Starts the application. */
+  public static void main(String[] args) {
+    SpringApplication.run(FeteApplication.class, args);
+  }
 }

backend/src/main/java/de/fete/adapter/in/web/HealthController.java

@@ -1,15 +1,16 @@
 package de.fete.adapter.in.web;
 
 import java.util.Map;
-
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RestController;
 
+/** REST endpoint for health checks. */
 @RestController
 public class HealthController {
 
-    @GetMapping("/health")
-    public Map<String, String> health() {
-        return Map.of("status", "ok");
-    }
+  /** Returns a simple health status. */
+  @GetMapping("/health")
+  public Map<String, String> health() {
+    return Map.of("status", "ok");
+  }
 }

backend/src/test/java/de/fete/FeteApplicationTest.java

@@ -1,31 +1,31 @@
 package de.fete;
 
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.web.servlet.MockMvc;
 
-import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
-import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
-import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
-
 @SpringBootTest
 @AutoConfigureMockMvc
 class FeteApplicationTest {
 
-    @Autowired
-    private MockMvc mockMvc;
+  @Autowired
+  private MockMvc mockMvc;
 
-    @Test
-    void contextLoads() {
-        // Spring context starts successfully
-    }
+  @Test
+  void contextLoads() {
+    // Spring context starts successfully
+  }
 
-    @Test
-    void healthEndpointReturns200() throws Exception {
-        mockMvc.perform(get("/health"))
-                .andExpect(status().isOk())
-                .andExpect(jsonPath("$.status").value("ok"));
-    }
+  @Test
+  void healthEndpointReturns200() throws Exception {
+    mockMvc.perform(get("/health"))
+        .andExpect(status().isOk())
+        .andExpect(jsonPath("$.status").value("ok"));
+  }
 }

backend/src/test/java/de/fete/HexagonalArchitectureTest.java

@@ -0,0 +1,63 @@
+package de.fete;
+
+import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.classes;
+import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.noClasses;
+import static com.tngtech.archunit.library.Architectures.onionArchitecture;
+
+import com.tngtech.archunit.core.importer.ImportOption;
+import com.tngtech.archunit.junit.AnalyzeClasses;
+import com.tngtech.archunit.junit.ArchTest;
+import com.tngtech.archunit.lang.ArchRule;
+
+@AnalyzeClasses(packages = "de.fete", importOptions = ImportOption.DoNotIncludeTests.class)
+class HexagonalArchitectureTest {
+
+  @ArchTest
+  static final ArchRule onionArchitectureIsRespected = onionArchitecture()
+      .domainModels("de.fete.domain.model..")
+      .domainServices("de.fete.domain.port.in..", "de.fete.domain.port.out..")
+      .applicationServices("de.fete.application.service..")
+      .adapter("web", "de.fete.adapter.in.web..")
+      .adapter("persistence", "de.fete.adapter.out.persistence..")
+      .adapter("config", "de.fete.config..");
+
+  @ArchTest
+  static final ArchRule domainMustNotDependOnAdapters = noClasses()
+      .that().resideInAPackage("de.fete.domain..")
+      .should().dependOnClassesThat().resideInAPackage("de.fete.adapter..");
+
+  @ArchTest
+  static final ArchRule domainMustNotDependOnApplication = noClasses()
+      .that().resideInAPackage("de.fete.domain..")
+      .should().dependOnClassesThat().resideInAPackage("de.fete.application..");
+
+  @ArchTest
+  static final ArchRule domainMustNotDependOnConfig = noClasses()
+      .that().resideInAPackage("de.fete.domain..")
+      .should().dependOnClassesThat().resideInAPackage("de.fete.config..");
+
+  @ArchTest
+  static final ArchRule inboundPortsMustBeInterfaces = classes()
+      .that().resideInAPackage("de.fete.domain.port.in..")
+      .should().beInterfaces();
+
+  @ArchTest
+  static final ArchRule outboundPortsMustBeInterfaces = classes()
+      .that().resideInAPackage("de.fete.domain.port.out..")
+      .should().beInterfaces();
+
+  @ArchTest
+  static final ArchRule domainMustNotUseSpring = noClasses()
+      .that().resideInAPackage("de.fete.domain..")
+      .should().dependOnClassesThat().resideInAPackage("org.springframework..");
+
+  @ArchTest
+  static final ArchRule webMustNotDependOnPersistence = noClasses()
+      .that().resideInAPackage("de.fete.adapter.in.web..")
+      .should().dependOnClassesThat().resideInAPackage("de.fete.adapter.out.persistence..");
+
+  @ArchTest
+  static final ArchRule persistenceMustNotDependOnWeb = noClasses()
+      .that().resideInAPackage("de.fete.adapter.out.persistence..")
+      .should().dependOnClassesThat().resideInAPackage("de.fete.adapter.in.web..");
+}

backend/src/test/resources/logback-test.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+  <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>%msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <root level="WARN">
+    <appender-ref ref="CONSOLE"/>
+  </root>
+</configuration>