feat: correx-managed model lifecycle slice 1 — config + manager factory + boot/shutdown

[[models]] config (ModelConfig/ModelsSettings) parsed by ConfigLoader;
InfrastructureModule.createModelManager + modelConfigToDescriptor; Main.kt
managed boot path spawns the default llama-server when [[models]] is present
(static [[providers]] path preserved when absent) and kills it on shutdown.

Plan: docs/plans/2026-05-31-model-lifecycle-management.md (slice 1 of 5).

infrastructure/build.gradle

@@ -28,6 +28,8 @@ dependencies {
     implementation "io.ktor:ktor-client-content-negotiation:$ktor_version"
     implementation "io.ktor:ktor-serialization-kotlinx-json:$ktor_version"
     implementation "org.slf4j:slf4j-api:2.0.16"
+    testImplementation "io.ktor:ktor-client-mock:$ktor_version"
+    testImplementation "org.jetbrains.kotlin:kotlin-test"
 }
 
 tasks.named("koverVerify").configure { enabled = false }