Add Phase 5 Kotlin desktop app: Compose Multiplatform with gRPC client

Kotlin/Compose Desktop application under desktop/ with:
- Gradle build: Kotlin 2.1, Compose 1.8, gRPC/Protobuf codegen, detekt
- ExoClient: gRPC client for both ArtifactService and KnowledgeGraphService
- Obsidian-style layout: collapsible tree sidebar, contextual main panel
- Five view modes: artifact detail, note editor, search results, catalog,
  graph (stub)
- Unified search bar with selector prefix support
- Command palette (Ctrl+Shift+A) for quick actions
- Menu bar with keyboard shortcuts (Ctrl+I/L/F/Q)
- Dark Material 3 theme
- Detekt lint config with Compose/test naming exceptions
- Unit tests for AppState and model types

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktop/build.gradle.kts

@@ -0,0 +1,97 @@
+import org.jetbrains.compose.desktop.application.dsl.TargetFormat
+
+plugins {
+    kotlin("jvm") version "2.1.20"
+    id("org.jetbrains.compose") version "1.8.0-alpha02"
+    id("org.jetbrains.kotlin.plugin.compose") version "2.1.20"
+    id("com.google.protobuf") version "0.9.4"
+    id("io.gitlab.arturbosch.detekt") version "1.23.7"
+}
+
+group = "dev.wntrmute.exo"
+version = "0.1.0"
+
+repositories {
+    google()
+    mavenCentral()
+}
+
+val grpcVersion = "1.68.0"
+val grpcKotlinVersion = "1.4.1"
+val protobufVersion = "4.28.2"
+
+dependencies {
+    // Compose Desktop
+    implementation(compose.desktop.currentOs)
+    implementation(compose.material3)
+    implementation(compose.materialIconsExtended)
+
+    // gRPC
+    implementation("io.grpc:grpc-netty-shaded:$grpcVersion")
+    implementation("io.grpc:grpc-protobuf:$grpcVersion")
+    implementation("io.grpc:grpc-kotlin-stub:$grpcKotlinVersion")
+    implementation("com.google.protobuf:protobuf-kotlin:$protobufVersion")
+
+    // Coroutines
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.9.0")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-swing:1.9.0")
+
+    // Testing
+    testImplementation(kotlin("test"))
+    testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.9.0")
+}
+
+// Protobuf code generation
+protobuf {
+    protoc {
+        artifact = "com.google.protobuf:protoc:$protobufVersion"
+    }
+    plugins {
+        create("grpc") {
+            artifact = "io.grpc:protoc-gen-grpc-java:$grpcVersion"
+        }
+        create("grpckt") {
+            artifact = "io.grpc:protoc-gen-grpc-kotlin:$grpcKotlinVersion:jdk8@jar"
+        }
+    }
+    generateProtoTasks {
+        all().forEach {
+            it.plugins {
+                create("grpc")
+                create("grpckt")
+            }
+            it.builtins {
+                create("kotlin")
+            }
+        }
+    }
+}
+
+// Detekt static analysis
+detekt {
+    buildUponDefaultConfig = true
+    config.setFrom(files("detekt.yml"))
+    parallel = true
+}
+
+compose.desktop {
+    application {
+        mainClass = "dev.wntrmute.exo.MainKt"
+
+        nativeDistributions {
+            targetFormats(TargetFormat.Deb, TargetFormat.Rpm)
+            packageName = "exo-desktop"
+            packageVersion = "0.1.0"
+            description = "kExocortex Desktop Application"
+            vendor = "wntrmute.dev"
+        }
+    }
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+kotlin {
+    jvmToolchain(21)
+}