chore(sidecar): wire grpc + protobuf-gradle-plugin + maestro

Generates Java stubs from proto/driverpb/driver.proto via the
protobuf plugin (sourceSets points at the shared root proto dir).
Pulls in dev.mobile:maestro-client:1.40.0, grpc-netty-shaded,
slf4j-simple, and the JUnit vintage engine so the gRPC test rules
work alongside JUnit Jupiter.

sidecar/build.gradle.kts

@@ -1,7 +1,10 @@
+import com.google.protobuf.gradle.id
+
 plugins {
     kotlin("jvm") version "2.1.21"
     application
     id("com.gradleup.shadow") version "9.0.0-rc2"
+    id("com.google.protobuf") version "0.9.5"
 }
 
 java {
@@ -14,15 +17,62 @@ kotlin {
     jvmToolchain(17)
 }
 
+val grpcVersion = "1.68.0"
+val protobufVersion = "3.25.5"
+val maestroVersion = "1.40.0"
+
 dependencies {
+    implementation("dev.mobile:maestro-client:$maestroVersion")
+
+    implementation("io.grpc:grpc-netty-shaded:$grpcVersion")
+    implementation("io.grpc:grpc-protobuf:$grpcVersion")
+    implementation("io.grpc:grpc-stub:$grpcVersion")
+    implementation("com.google.protobuf:protobuf-java:$protobufVersion")
+    implementation("javax.annotation:javax.annotation-api:1.3.2")
+
+    implementation("org.slf4j:slf4j-simple:2.0.16")
+
     testImplementation(kotlin("test"))
+    testImplementation("io.grpc:grpc-testing:$grpcVersion")
+    testImplementation("io.grpc:grpc-inprocess:$grpcVersion")
+    testImplementation("junit:junit:4.13.2")
     testImplementation("org.junit.jupiter:junit-jupiter:5.11.3")
+    testRuntimeOnly("org.junit.vintage:junit-vintage-engine:5.11.3")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher:1.11.3")
+}
+
+protobuf {
+    protoc {
+        artifact = "com.google.protobuf:protoc:$protobufVersion"
+    }
+    plugins {
+        id("grpc") {
+            artifact = "io.grpc:protoc-gen-grpc-java:$grpcVersion"
+        }
+    }
+    generateProtoTasks {
+        all().forEach { task ->
+            task.plugins {
+                id("grpc")
+            }
+        }
+    }
+}
+
+sourceSets {
+    main {
+        proto {
+            srcDir(rootProject.file("proto"))
+        }
+    }
 }
 
 application {
     mainClass.set("dev.uatu.sidecar.MainKt")
 }
 
+// JUnit 4 (vintage) for the gRPC GrpcCleanupRule + JUnit 5 (jupiter)
+// for the rest. UseJUnitPlatform with the vintage engine handles both.
 tasks.test {
     useJUnitPlatform()
 }